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  1. #1
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    Default Modifications for precision rifles

    I’ve recently spoken with some people who have been interested in tactical rifles and the reasoning behind some of the modifications made to actions, barrels, etc. I wanted to try to answer this question with some depth, but not too much for the people who aren’t necessarily interested in becoming home gunsmiths. I am NOT a gunsmith, but I sit in the shop and work with friends that are, and I have assisted in building my own rifle from the ground up. I’m familiar with all of the processes and at least one way to do them, and the reasoning behind it. I want to point out that some of these techniques don’t have a “set” way to do them, although the principles behind them are usually similar. So… just because you don’t see something done in a specific manner doesn’t mean it’s not correct or “true”. Keep in mind by tight tolerances we’re talking about thousandths of an inch and sometimes even a couple of ten thousandths, depending on the smith, applications, equipment, etc; very small amounts.

    I’ll talk in vague terms regarding effects on the action and accuracy because some of these issues are even debated amongst top smiths of the WORLD. I’m going to talk mostly in terms of the Remington 700 action because it’s one of the most customized actions for tactical rifles in the United States; it’s also the one that I’m most familiar with. Some other actions may not need the techniques commonly done to the Remington 700, and others may need different techniques done to them in order to reach favorable results. I hope this brief overview helps you understand some of the terms and particulars.

    Always remember that in order to have an accurate rifle, you MUST have consistency. There shouldn’t be any stress or binding in any part of the setup, as well as no movement or wobble of the action in the stock. The process of “blueprinting” that I will describe will help ensure that. Blueprinting is a term that is often used to mean “cleaning up the tolerances of the action”. Because barrels, actions and other parts are often made on an assembly line with the expectation that parts need to mate closely with other parts, there must be looser tolerances than optimum and some “slop” so that these parts always fit together without costly custom fitting of every firearm. This little bit of slop does hurt accuracy on the most minute levels and results in a slightly “loose” fit in terms of precision machining. It’s not something you’d typically make out with your eye or by feel, but you can see it once you have these parts in a lathe and spinning. The goal is to have everything on the receiver square, but not only square, but concentric and “true” to everything else on the receiver. These terms may seem a little vague now, but I’ll be elaborating shortly.

    When you remove the barrel from an action/receiver on a Remington 700, there are threads on the interior part of the action and the barrel threads in. The outside edge of the receiver (the face), makes contact with a recoil lug (more on that later) that contacts the barrel. This face needs to be square (perfectly flat), so that the barrel can make even contact with the entire receiver. This is the joint where the separate parts become one, so it needs to be perfect. Even contact ensures that the barrel doesn’t point, wobble and rock to any one side, and it needs to have a large, even area to distribute the forces and harmonics acting on the barrel and action. Barrels and actions “ring” the way that a bell does, but it tends to be on a level that we can’t hear. Consistent and even harmonics make for consistency and accuracy. An even face also means that there is no pressure or stress added to the barrel or action, because pressure is evenly distributed over the whole face of the action.

    After the face is squared off, the next usual step is to work the integral lugs of the receiver and the threads. The integral lugs are on the inside of the receiver, and they are the flat area that your bolt lugs (ears that stick out on the bolt toward the chamber) make contact. It should be noted that the bolt lugs also have to be cleaned up so that they are also flat, but we’ll get into that later. Again, the goal of squaring up the integral lugs is that the bolt makes flat even contact with the action. This is basically the “seam” where the bolt and action become one. The lugs have to be parallel and true with each other, so that the bolt makes even contact, this is important for several reasons. If the bolt does not make even contact with the receiver, it will sit “cock eyed” in the action. This means that the bolt is actually not quite in a straight line with the chamber that is reamed in the barrel, and when the brass is pushed back on the bolt face during firing, only 1 lug will bear the brunt of the tremendous pressure. This can effect harmonics, can induce stress, and cause the bolt to “settle and shift” while the bullet is still traveling down the barrel. This will effect where the bullet impacts, and how consistent the rifle is. In factory rifles, there is actually a fair bit of slop on the lugs; it doesn’t usually cause extraction issues, but in some cases it can, and it also can be hard on brass.

    The other technique that is commonly done at the same time as squaring up the receiver face and integral lugs is the process of cleaning up the receiver threads. The threads can be thought of as the “glue” that holds the action and the barrel together. They must be clean so that the barrel doesn’t wobble, and so that ALL of the threads make good even contact. This kind of seems like a small deal to most people, but it’s very important. If the barrel wobbles or shifts, it will obviously make the rifle inconsistent and it will change the alignment of everything else in the rifle. You want all the threads to make even contact so that there is not any stress added to the barrel (especially around the chamber area), and so that the harmonics are again even and consistent between the barrel and the action; they must be mated as close to perfect as possible. One thing to keep in mind is that the threads not only have to be clean, but they also have to be concentric and true to the receiver face and the integral lugs; ALL THREE THINGS. If the threads are not square to the receiver face, it could be impossible to tighten the barrel up to the action and square off the face; or if you happened to do it, the threads would be ruined and wobble after that. IF you did manage to do it because the threads weren’t that far off, you could induce a GREAT amount of stress into the barrel around the chamber. This stress can shift and change as the barrel starts to heat up (which it does easily in this area where pressures are very high), and/or if you ever take your barrel off. This is because you will tighten it differently and the stresses will also change in the chamber area. All of this leads to inconsistency and stress; which are what you are trying to eliminate.

    The receiver is faced off, integral lugs faced off, and threads cleaned up or redone all without the receiver ever coming out of the lathe. It can take some work to get a receiver to spin perfectly true in the lathe, and once you have it in right, you want everything to be “concentric” to the other parts. You want all of these things to be true and in EXACTLY the same line (which is straight). This keeps everything lined up, so that the bore of the barrel, barrel, action, bolt, firing pin, etc all line up perfectly. This not only makes them become one piece, not just several pieces slapped together; it also helps them have no extra stress added to them and have good consistent harmonics. Here is a link to a prominent tactical rifle smith who talks about his process that he goes through to true up the receiver and the bolt. http://www.louisianaprecisionrifles....eprinting.aspx He is not the only smith or necessarily the “best smith” (there are lots of GREAT smiths, including William); he merely had this up handy in an easy to read manner so I posted it here. Here are also some embedded links so that you can see the process occur and maybe understand it a little better.


    Last edited by Tomcat088; November 4th, 2009 at 08:44 PM.

  2. #2
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    Default Re: Modifications for precision rifles

    Once the receiver has been trued up and everything is concentric, the smith will usually go to work on the bolt. The videos that I will post talk about “sleeving” the bolt, which we will cover more in-depth later. I won’t address it right now as it’s not always done to tactical rifles.

    There are a few things that are always done to bolts after the action has been blue printed. These techniques mainly concern the bolt lugs and the bolt face. The lugs on a factory bolt are not usually perfectly square, and/or sometimes one lug will actually be slightly longer than the other one. This results in uneven contact between the bolt lugs and the integral lugs of the action. The uneven contact causes the bolt to sit at a slight cant, meaning it’s not perfectly lined up with the chamber, which affects harmonics. Since the bolt face will also be on a slight angle, it will also effect how the bolt face mates up with the chamber and this induces some stress on the chamber area. The stress will affect the brass and harmonics, and some people believe the seal of the bolt face affects the pressure curve that occurs within the chamber. What it comes down to is… if you’ve taken the time to make the integral lugs square, you need to true up the bolt lugs to get them to make nice even contact. This area that needs trued is actually at the BACK/REAR of the lugs, the part of the “tabs” that is closest to the bolt handle; the front of the lugs make contact with the rear of the chamber area and are part of Remington’s “3 rings of steel”. The face (very front edge of the bolt) is also squared up so that it will make even contact with the chamber that will be bored in the barrel. Everything being square allows for perfect alignment of the system, making it basically one piece; and it also allows for a good seal with the chamber (safer due to more contact), and allows a nice flat bearing surface for the lugs (less stress on the action, even pressure curve, and safer due to better consistency).

    It should be noted that when you change how the lugs contact the integral lugs for a rifle that is already chambered, you actually change the “head spacing”. I won’t get into the concept of head spacing a great detail at this time, but I do need to mention it due to safety concerns. If you true up the lugs on a rifle that is already chambered, you MUST check to make sure that it is properly head spaced. It could be dangerous, and possibly even FATAL to not ensure this. The lugs are what stop the bolt as it travels backwards from the pressure of the cartridge going off, if it is allowed to travel rearward too far it could allow the brass to get out of the chamber area and expand/explode; which may or may not make the action explode. Not having a rifle that is properly head spaced is a way to make a rifle into a grenade, so it’s VERY important that a rifle MUST be head spaced correctly, you can’t just true up the lugs and throw it all back together to shoot.

    There are quite a few options and modifications that are sometimes done to bench rest rifles (the most accurate rifles in the world) that carry over into tactical rifles, but for the most part, tactical rifles do not need extremely specialized methods to get results that are acceptable. If you throw a good quality barrel (chambered properly) onto an action that has been blue printed with the bolt trued, and with a quality reload; you WILL have a .25-.5 MOA rifle. Keep in mind that this type of accuracy and consistency is dependent on the shooter, gunsmith, and reload, and there are a few exceptions, but you will almost always have a very consistent and accurate .25-.5 moa rifle. Lots of people will TALK about how their stock rifle always does this, and most of the time it’s just that…..talk. A CONSISTENT .5 moa rifle (especially out past 300 yards) is not very common, and doesn’t usually happen with factory rifles (TRUE factory/shelf rifles, not $1,000+ semi-customs). Keep in mind we’re not talking about 3 shot groups, we’re talking about 5 and 10 shot groups. You need more than three shots to even begin to talk about real CONSISTENCY. For MOST people’s applications, going beyond these steps in terms of customizations has VERY diminishing returns, especially when you can buy a custom action that doesn’t have to have these things fixed for only a couple of hundred dollars more (as a starting place).

    Beyond what has been mentioned above, there are some other nice additions that can be done, but may not be as beneficial or necessarily as cost effective. A bolt modification that is done semi frequently, that is relatively cheap, and can have some noticeable benefits is changing the firing pin. Most of the people that change the firing pin will go with a partial aluminum or custom steel pin like a Tubbs firing pin that is lighter than the stock unit. Since the firing pin is lighter, it needs a stronger (not physically heavier) spring so that it strikes the primers hard enough to set them off. The reasoning behind exchanging the firing pin for a lighter one has to do with “lock time”. Lock time is the time that it takes from when the trigger breaks, to when the firing pin actually strikes the primer; it is a VERY brief time and is measured in milliseconds. The idea is that the faster that the firing pin hits the primer and gets the bullet down the barrel, the less time that the shooter has to move/shift/flinch and screw up the point of aim. Most of the firing pins and bolt shrouds advertise somewhere around a 40% decrease in lock time, which is fairly significant; especially considering that a Remington 700 has the fastest lock time of all the bolt rifles. Personally, I’ve never noticed any kind of difference in shooting at stationary targets. I’ve also never shot at movers with a factory firing pin and got dope (adjustments to compensate for lead and drop) and then went to shooting the same movers with a gun using a lighter firing pin and had to use different dope. Some people say that it DOES reduce your hold for movers, but don’t have experience with both firing pins in the same rifle. Plenty of bench rifle guys don’t like these firing pins because they believe that the pin doesn’t resonate the same as an all steel firing pin (it’s made of aluminum in the rear and the tip is steel). Some tactical rifle guys do not like them because it requires a heavier spring; they believe that it could result in a rifle that is not as reliable because it could have light primer strikes. I do have this modification in my rifle, and it should be noted that if you change your firing pin you MUST check the protrusion of the firing pin. I checked mine before I took it out shooting and it was sticking out WAY too far; which can result in breakage, pierced primers and a resulting potentially unsafe condition. I have yet to see the firing pin modification have any significant impact on the rifle (good or bad), but it can be a little piece of mind and may give you just a slight edge (even if it’s mental); since it’s fairly cheap if you would like to do it, go for it. In terms of accuracy, only a few people in the world can shoot well enough to notice the difference between how a steel or steel/aluminum firing pin resonates.

    A process that is occasionally done to tactical rifles, and many times done with bench rifles, is “bolt sleeving”. The action has an area cut out in it that the bolt travels down as you cycle it called the bolt raceway. Since we have lots of mass produced parts, there has to be some slop in the raceway so that the bolt travels easily down the raceway and isn’t binding or getting stuck. The bad part is that usually this slop can be a fair bit and the bolt kind of wobbles back and forth and slightly snags as it is being worked forward and backwards; this makes the bolt feel sloppy, slightly effects the speed at which you cycle the bolt, and on rare occasion, can effect how the rifle feeds. The problem is fixed by increasing the diameter of the bolt so that it fits tighter in the raceway, and doesn’t wobble around as much. This is addressed initially by the gunsmith boring out the bolt raceway and making it larger. This seems like the opposite of what you want to do, since you want to tighten the fit of the bolt, but it is done so that the entire raceway is a consistent diameter and “true”. After the raceway is bored, the factory bolt is “sleeved”. This means that they take the bolt and turn it down so that it’s a little smaller and has a consistent diameter. A sleeve (metal tube) is then cut so that it will fit over the original bolt, but has a larger diameter than the bolt raceways. The gunsmith will then turn this larger bolt down so that it’s only about one thousandth of an inch smaller than the bolt raceway, although it is sometimes more or less depending on what the customer wants. Sometimes instead of even messing with the factory bolt, a smith will use a custom bolt that is larger than the factory bolt, and turn it down to the correct diameter. The benefit of doing it this way is that you have a one piece bolt that doesn’t have any seams or places where it COULD fail (sleeved bolts, don’t usually fail anyway); the custom bolts are also fancier and very handsome pieces of work. The result is a VERY clean smooth feeling bolt that is easy to run. This sounds GREAT to most people, and makes them ask, “Why you wouldn’t this to every rifle?” As with all things, there can be a drawback to this process. The “slop” in the bolt raceway doesn’t always feel the best, BUT it means that grit and grime in the raceways will not keep the bolt from functioning properly. Tactical rifles are not usually cared for the way that bench rifles are, some of them are put through VERY harsh conditions like mud, water, sand, not cleaned, etc, etc. A really tight bolt raceway doesn’t leave anywhere for all this grime to go, and can result in bolts binding up and not wanting to feed or move rearward. Since there can be a fair bit of cost in buying a custom bolt or having your bolt sleeved, it’s not usually worth the cost to have your bolt sleeved for just a little bit of added smoothness; it’s just not much of an advantage if you want the rifle to not be as sensitive to malfunctions in “field conditions”.

    There are a few other bolt modifications that are sometimes done to bolts on tactical rifles, although they’re not necessarily the norm. Some people like to have a different bolt handle put on their rifle so that it’s longer, a different style, clears the optics better, etc; while others simply want their bolt handle to be better attached to their rifle. They have their handle removed, and then sometimes welded back on, or brazed/soldered and pinned (screwed into the bolt body). This means that your bolt handle could, theoretically, take more abuse when you are pulled or slamming it (which you shouldn’t be). There are a few arguments against having this modification done, and most of them just relate to practicality. It is VERY rare for a standard Remington 700 bolt handle to break off. They’re attached pretty well. If you are pulling or shoving so hard on a bolt handle that you might break it off, you usually need to stop what you’re doing and take your rifle in to be serviced; pushing or pulling harder is not going to fix the issue you have. If you have a piece of brass that is being so stubborn that it won’t extract with a standard bolt handle, the extractor will usually tear through the brass before the bolt handle breaks off. It’s kind of one of those modifications that will give some people more piece of mind, although it probably will not effect your rifle in a bad or good way. If it makes you feel better, do it, if it doesn’t really bother you, leave it alone.

    A final modification you may see that is sometimes done to bolts is the process of changing the “timing”. The reason that a bolt’s timing is changed is for one of two reasons; either the camming action of the bolt is off/out of phase of where it should be, or the lugs and the bolt are not correct. In the first instance, which is quite rare, the lugs are not in proper alignment. This does not usually occur unless some bad gunsmith has worked with the rifle and messed with the timing so that the lugs do not close all the way with the integral lug of the action. This is DANGEROUS, and can result in hot gases, powder and/or brass being pushed between the gap of the lugs and into the shooter’s face. Again, this usually only occurs if the bolt has already been messed with by an unqualified gunsmith.

    The second reason does happen more frequently, and it’s related to the “cam”. As the bolt is raised, when it is almost at the peak, it begins to cam, which means that it actually pushes itself back just a little bit. This is a feature that is designed into the bolt that assists in the beginning of extracting the cartridge. Occasionally a bolt will come from the factory that doesn’t have much cam, or no cam; if it is missing a little cam, it’s not usually a big deal. If the rifle has no cam, or has trouble with extractions, THEN a gunsmith will sometimes decide to remove the bolt handle from the bolt body and reattach it to get back the cam. When a new custom bolt is added to the rifle, it has to be timed properly, OR if the bolt handle is removed from the bolt body, it needs to be timed properly. Either way, this is not a modification that typically happens with Remington rifles because they usually have enough cam to extract reliably.

    There are a few other modifications to the bolt that I could get into like truing up the firing pin hole (usually done while sleeving), using Sako extractors in a Remington action, etc. I’m not really going to get into those modifications unless people are really interested in them. For the most part, the most common and necessarily modifications have been listed. Here are a few videos that talk about boring the raceway in the action, truing up the lugs, bolt sleeving, and even repairing a bolt that was improperly timed and had no cam.






    Last edited by Tomcat088; October 25th, 2009 at 06:16 PM.

  3. #3
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    Default Re: Modifications for precision rifles

    Now we have the action and bolt taken care of, but we’re missing a very important part of the entire system; the barrel. The barrel is an extremely important part of the rifle, possibly the most important because it’s what actually directs the bullet on target, and the last part of the rifle that actually contacts the bullet. There is a wide amount of information we need to cover about barrels; different ways that they’re made, contours (diameter and taper), chambering, fluting, stress relieving, etc. I’d like to provide this link from Dan Lilja of Lilja barrels, to help you understand the processes of barrel making, and he gets into it in a little more detail if you’re curious. http://www.riflebarrels.com/articles/barrel_making.htm and http://www.border-barrels.com/articles/bmart.htm

    Barrel material is usually chosen for a variety of reasons and applications that consider machinability, strength, durability, ability to be blued, etc. Barrels that can shoot well can be made from several of types of steel, and quality manufacturers will give you options that will always shoot well, the preference in details is up to you. When purchasing a barrel, it’s important to at least have an idea on the application of the rifle, so you have an idea of what type and weight of bullets you will be shooting. Some initial things to consider are weight of the rifle, overall length, velocity requirements and what type of bullets you want to utilize. You also need to consider twist rate. Most of the time, the twist rate of your barrel will depend on which weight or length of bullet that you will typically be shooting from the barrel, how fast you will be pushing that bullet, and caliber diameter. Faster twists (a compete twist in a shorter amount of distance) tend to prefer longer/heavier bullets and slow twists will favor lighter/shorter bullets. This varies by caliber and while a twist rate of 1:12 may be “slow” in one caliber, it may be relatively “fast” in another.

    The length of the barrel will be determined by your velocity requirements as well as how you need the rifle to balance, handle, and your expectations for its overall length. For example, large magnums often need slower powders to achieve high velocities and this requires longer barrel lengths (sometimes in excess of 26”-28”). However, barrel length itself is not an iron clad indicator of accuracy and shorter/stiffer barrels can perform as well, if not better, that their longer counterparts under the right conditions. Those considerations, along with the powder that one will be using and it’s minimum burn length will typically help choose the barrel length; so it’s also advantageous to have some of this in mind before you choose a barrel to start with.

    The “contour” of the barrel has to do with the starting and ending diameters of the barrel, and how it tapers between those two diameters. Most precision rifles will have heavy barrels, although tactical rifles will have lighter contoured barrels than bench rifles. The main reason behind this is because bench rifles are carried to the bench and not moved around much; tactical rifles are carried, ran with, and moved to various shooting positions, so they can’t be unbearably heavy or long. You will hear of lots of different tapers like “MTU”, “Sendero”, “Heavy Varmint”, “18”, etc. etc. Different companies will have different systems for naming, and different dimensions on barrels. All precision rifle barrels are heavy for a few important reasons. One of the reasons has to do with stability and stress as a barrel heats up. The larger the diameter of the barrel, the more rigid and stiff it will be; this means it doesn’t “whip” (oscillations in the barrel that can be imparted to the bullet), but this comes at the sacrifice of weight. A heavy barrel also takes more time to heat up. Heat can impart stress on a barrel as well as decrease the efficiency of the chamber and barrel. As a result, any stress that it does have in the barrel takes longer to show up with more metal and surface area to transfer heat to/from. There are basically two schools of thought on barrel length; “short and fat” or “fairly heavy and long”. Both of these approaches work well and have their costs and benefits. A “short and heavy” barreled rifle (20” or so) will usually balance well, and you don’t have a long barrel to knock on things, so they’re easy handling. The draw back to this approach is that you lose velocity, and in some calibers it can be difficult to stretch the shorter barrels to 1,000 yards or more without pushing your reloads HOT. On a “fairly heavy and long” barrel you get the benefit of plenty of velocity and not having to push reloads, which increases barrel life. Although the barrel isn’t as heavy, it doesn’t heat up as fast because you aren’t pushing reloads as hot. Longer barreled rifles will not be as “handy” because you typically have a 24-26” barrel; they can sometimes be a bit “front heavy” if the barrel length isn’t considered while designing the rifle. For most people’s uses and conventional calibers (non magnum), a 20-22” barrel will usually work well. Ask LOTS of questions of the barrel makers, they are more than happy to answer all of your questions honestly and with great wisdom; also get out and handle some different contours of barrels and lengths, and see what you like. Quality barrels are expensive (usually $300-400 BEFORE all the gunsmithing), so it’s important to try to get it right the first time.

    Once we have an idea of what we expect from the barrel we can look at the specific attributes of the barrel itself. Barrels begin their life as a “blank”. This “blank” is a steel cylinder that has a perfectly straight hole drilled through it slightly smaller than the desired caliber; it is not yet a “barrel” as it is smoothbore, unrifled and has no chamber cut. “Riflings” are the grooves (low spots) and lands (high places) that are inside of a barrel that place spin on the bullet so that it is gyroscopically stabilized in flight. The rifling is VERY important, particularly in its concentricity and uniformity along the length of the barrel. It is VERY important the rifling is consistent in its height (cutting surface into the bullet); the bullet MUST make a good seal with the lands and grooves to maintain pressure, and it needs to be cut deep enough to reliably impart spin on the bullet. It is also very important that the twist rate of the barrel stays VERY consistent throughout the length of the barrel. The twist rate CANNOT decrease down the length of the barrel, although it is not detrimental to accuracy if it slightly increases. If twist rate ever decreases in a barrel, it widens the grooves that are cut into the bullet; this causes the bullet to chatter and wobble as it moves down the barrel, which has an effect its stability, spin, seal, etc. If the twist rate slightly increases, it’s ok because the grooves are never cut wider in the bullet, so it therefore keeps a consistent seal, twist, and stability. A truly constant twist rate will not shoot any worse than a twist rate that slightly increases. There are basically 2 methods to add the rifling to the barrels, which we will cover shortly. For more on some things that make barrels shoot, you can look here at another Dan Lilja article. http://www.riflebarrels.com/articles...l_accurate.htm

    Almost all factory barrels are made from “button rifling”, although a few companies “hammer forge” barrels. Hammer forged barrels are almost never used on precision rifles because of the stresses induced in the forging processes. In “button rifling”, a piece of metal that is football shaped called the “button” is inserted into the hole and pushed or pulled through the hole. The button is slightly larger than the hole in the barrel, and it has the exact dimensions for the lands and grooves in it; twist rate is determined by how it is turned as it is pushed/pulled through the hole. Since the button is larger than the diameter of the hole in the blank, the metal is forced to move and conform to the button, but it is NOT removed from the barrel. The result is the rifling is formed into the barrel. The barrel is then typically cut down to the UNFINISHED length, and then turned in the lathe to the proper contour (taper) of what the customer has ordered. The barrel isn’t turned or cut until AFTER the rifling has been added because it displaces a small amount of metal, so the blank stretches or gets slightly larger in the process. The rifling is then usually hand lapped (polished), so that it is nice and smooth. All quality barrels are then stress relieved, which is usually through a cryogenic and heat treat process (more on that later).

    In a “cut rifled” barrel, the blank is identical before the rifling, in that it is a piece of steel with a very straight hole drilled through it. In the cut rifling process there is no button; instead a cutting tool is drawn through the barrel to cut out the desired groove, and it spirals in the desired twist rate. This is a VERY slow process, for several different reasons. The grooves are cut 1 at a time, and only 1/10,000th of an inch at a time; that wasn’t a typo, that’s one ten thousandth of an inch. One groove is cut for one pass, and then the barrel is turned slightly to where the next groove will be, and then a pass is made for that groove. This means that it takes 10 passes to make the grooves one thousandth of an inch deep, with most grooves being around 5 thousandths. When you consider a barrel may have 4 or 6 grooves, we’re talking about 200-300 passes; a VERY slow process indeed. The barrels can be turned to the desired diameter and cut to the unfinished length before or after the rifling is added because the barrels do no stretch or change in any way. The barrel blank is then hand lapped like the button rifled barrels are. Again, all quality barrels are then cryogenically and heat stress relieved.

    For some more specifics and information on button rifling and cut rifling, you can look here.
    http://www.riflebarrels.com/articles...fle_barrel.htm
    http://bettincustomguns.com/Technica...techniques.htm

    Some will ask, “Why different processes, and what are the benefits of one over another?” I will first start off by saying again, BOTH of these processes result in great barrels that shoot, and that are similarly priced. When the button is drawn through a barrel blank, the metal is moved and pressed into shape, this does several things to the barrel. One thing that can occur during this process is sometimes the steel does not move uniformly, this can result in an area where the diameter of the projectile hole has slight variation. This may not have any effect in some cases, but it can often be great enough that it can cause the bullet to not have even support in the rifling, and will cause gases to vent around the bullet because the seal is slightly broken. Uneven pressure (gases) going around the bullet can cause instability, or at the very least cause you to lose some muzzle velocity. Another drawback to the button rifling process that occurs is that a great deal of stress is added to the steel while the rifling is being added. Keep in mind that the steel is being pressed and moved to form the rifling. For this reason, it’s VERY important to have a button rifled barrel properly stress relieved. After they are properly stress relieved, they don’t usually have much more stress in them than a cut rifled barrel. One of the benefits of a button rifled barrel is how quickly they can be made, so the lead times (wait time) are usually shorter than a cut rifled barrel. One would think that this would make them cheaper, but that’s not usually the case. All of the quality manufacturers keep tight quality control standards on their barrels, and you don’t really have much worry about large variations in diameter, etc.

    Cut rifling is a nice process because the result just from the rifling needs very little polishing and is VERY consistent and concentric. The process introduces NO stress into the barrel, so this means that stress relief is not as critical on these barrels, but all quality manufacturers still lap and stress relieve their cut rifled barrels. One of the drawbacks to the process is how long the process takes, and as a result if you order a barrel from the manufacturer that is not already stocked by someone, the lead time can be great. Four months is a pretty typical lead time for cut rifled barrels. Other than the wait time, there is not really any drawback to cut rifled barrels. Sometimes cost is a little greater than if you would go with a “cheaper” button rifled manufacturer, but typically the quality barrel makers will have similar prices, whether using a button or cut rifled process.

    I will say again that NEITHER of these processes is necessarily better than another, both methods have resulted in world record setting rifles. Usually one barrel maker will only use one type of process to make barrels, either button or cut rifled barrels. Top barrel makers in the world include (in no particular order) Krieger, Shilen, Broughton, Bartlein, Lilja, Hart, Pac-Nor, Lawton, Lothar-Walther, Rock, Brux, Border, Spencer, and many others. If you’d like to see some of these manufacturers and more information about the makers and their processes you can find it here. http://www.6mmbr.com/barrels.html . I won’t get into this too much unless others are more curious about it, but some of these manufacturers specialize in different types of barrels, for different sports, styles of rifling (polygonal, radiused, etc), number of grooves, gain twist, etc.

    So you now have a “barrel blank” with rifling, in the caliber you have chosen, from a quality manufacturer; now what? Well, as bad as it hurts to say, the barrel still needs LOTS of work (and money) before it will ever go onto your rifle and be a shooter. The barrels usually come an inch or two longer than your desired finish length; the reason being that you want to saw off the bits that have tooling marks from the rifling process so that the bore is nice and smooth.

    The first and MOST important thing that the smith will do is get the barrel to turn PERFECTLY true in the lathe. The interesting part about this process is that it is NOT measured or done from the outside diameter of the barrel, but by the inside bore diameter. The reason that it is done this way is so that everything lines up perfectly; it wouldn’t matter if the cartridge was in line with the outside diameter of the barrel if it was NOT lined up with the bore in the barrel. This would mean that the bullets would be going into the lands and grooves on an angle, and the barrel would never shoot to its full potential. There is very little margin of error for getting the barrel to turn true, the hole in the bore is long and any error will increase as the bullet gets further and further down the barrel.

    The gunsmith will also measure your action that s/he has blueprinted, and will know the EXACT diameter of the threads of the action, and the tenon length (where the barrel screws in). The gunsmith will start to turn the barrel and cut the threads on the barrel so that they are a tight, even and clean fit into the action, and so that they are also the right length to match up to the action. On Remington 700’s there is a recoil lug that sits in the stock to absorb the recoil, and keep the action from sliding in the stock. It’s always a good choice to buy a quality aftermarket lug (usually wider for more stability), so that the face of it is square. The barrel passes through the recoil lug (tab hangs down and sits in the stock), and it sits between the action and the barrel. Since the action face is square, and the barrel will be cut square, it’s important for the recoil lug to be square so they make even contact where no stress is induced and they essentially become one piece.

    Once the threads are put on, the gunsmith will usually go to “chamber” the barrel for the cartridge that you have chosen. Up until this point, the barrel does not have a place for the “brass” to go; it is merely a barrel that has a hole through it that is the size of the bullet, nothing else. Again, the barrel MUST be spinning PERFECTLY true relative to the bore; it’s of the UTMOST importance. There are different ways to chamber a rifle, all of them work if the smith is competent and has the barrel spinning true. The gunsmith will then pull out the “reamer”, which is basically a very precise drill bit that is shaped exactly like the chamber of cartridge that you want your rifle to be. With the barrel spinning, the gunsmith VERY carefully starts to slip the reamer into the hole, and it cuts away the extra metal that is in the chamber area. This is a very painstaking process and it has to be PERFECT. If it’s not, the rifle can be unsafe, or will never be accurate. The gunsmith will go to his measured depth for the chamber and remove the reamer, then he will start to “counter bore” the barrel. The “counter bore” is the place just behind the chamber where the front side of the bolt lugs makes contact with the barrel. It is part of what Remington calls their “3 rings of steel”, and it matches perfectly flush and stress free with the bolt lugs. The gunsmith will go through a painstaking process of every so slightly moving the counter bore, stop the machine, and thread the barrel onto the action (usually still in the lathe). They will then place the bolt into the action and see if the rifle is properly head spaced (they have a gauge). If the rifle is not properly head spaced (hopefully not enough room for the bolt to close), they will remove the action and cut the counter bore just a little bit deeper. They will go through this process until the rifle has just the right amount of head space. They will then very gently polish the chamber area, but NOT the neck and throat area of the chamber; it’s too easy to mess it up and get into the lands (they must be perfect for precision). We’ll get into what happens later as a result of not polishing the neck and throat area. (Everybody can now stop holding their breathe, lol, it’s a nerve wrecking moment sometimes.)

    The hard part is over, and now the smith will take the rifle out of the lathe and turn it around so that we can crown the barrel. The “crown” is the last part of the barrel that touches the bullet; it needs to be sharp (no dings), even so that it vents gases in a uniform way, and clean (no burs). Some people like target crowns of various degrees (9, 11, etc), and some people like “stepped” or “recessed” crowns. The goal of the crown is to protect this area so that it doesn’t receive dings, burs, etc. Both of the types of crowns will do the job fine, and it’s a preference thing. The typical “style” on tactical rifles is a recessed crown that is finished at 90 degrees, or has a slight angle on it. Tactical rifles usually see slightly rougher conditions; if something contacts the top of the barrel you have a flat area that can stop the object from touching the bore, and doesn’t direct it towards the crown. With an 11 degree target crown, the entire face slopes towards the crown; this means that if something comes in contact with the slope it will be direct down towards the crown. However, the 11 degree crown does allow gases to escape in a very uniform manner and is common on competition rifles. Either way, if the muzzle is set on something hard (which you really shouldn’t do); either of these crown styles will serve to offer some protection to the crown.
    Last edited by Tomcat088; June 6th, 2010 at 01:01 AM.

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    Default Re: Modifications for precision rifles

    So now that the barrel is all finished, the recoil lug is placed over the threads and the barrel is threaded into the action and checked for proper head spacing. The barrel, recoil lug, action and bolt are now sitting in perfectly alignment, stress free (hopefully), and making full and even contact. For all practical purposes, the rifle can be slapped in a stock and is ready to go, although other modifications can be made and will be discussed.

    Most of the modifications that can be done to the barrel are specifically related to the chamber and its dimensions. Some of you may have heard of “Ackley Improved” or “A.I.” chambers. The chamber is cut so that the shoulder is further up on the brass (towards the neck), and it has a different angle. The reason for doing this is so that you can get more velocity because you have a slightly increased case volume, and so that the brass does not “run” and get worn out as easily. You will typically see A.I. chambers in custom made hunting rifles (especially varmint rifles), and on bench rest guns; it is NOT common practice to have tactical rifles chambered in A.I. (sometimes it happens). Tactical rifles must be shot a lot to get your dope (lead, and drop compensation), when you do this with hot reloads you get more barrel wear; you don’t want to wear out a barrel that you just got the dope for, and that is expensive.

    Another modification that you may have heard about is called “tight neck”, or “tight necking”. On a normal chambering, there may be .008” between the chamber neck and the brass. When you “tight neck” a chamber, it is cut so that there is usually only .002-.003” between the chamber neck and the brass. The reason for doing this is so that the bullet is introduced to the rifling in a more consistent and straight line. Tight necks are usually done ONLY on bench rifles because they are a pain in the neck (pun intended), and require for every single piece of brass to be neck turned. When you neck turn brass, you shave it so that it has a consistent diameter and thickness throughout the neck. This is a time consuming and tedious process, and not something that most tactical rifle shooters want to deal with. The gains in accuracy are VERY slight, and usually beyond most people’s needs (unless in competition), and beyond most people’s capability for accuracy. There is a very obvious reason that this is almost NEVER done to tactical rifles. When you make the tolerances this tight in the neck area, there is VERY little room for any kind of dirt or debris. So anything entering the neck area will keep the rounds from chambering properly, and just “jamming” the round in will only cause more problems.

    There is one chamber modification that is semi-frequently done to tactical rifles; it’s called “long throating”. The “throat” area of a rifle is the area past the neck where the bullet sits just before it enters the rifling. This is the area that begins to wear and that reloaders “chase the lands” so that they get the best accuracy, because it is eroded after enough shooting (thousands of rounds). Standard chambers and throats typically work great with almost all ammunition, but with some bullets it’s not optimal. Many long range and tactical shooters like to shoot long and heavy bullets that are sometimes called VLD’s (Very Low Drag) bullets, or they have a similar profile to VLD’s. VLD bullets are very aerodynamic, which assists in wind calls over long range, and they owe part of that to the fact that they are heavy and very long. As a result of their length, in a standard throated rifle, they will sometimes already be touching the lands (meaning they can’t stick out further), but LOTS of bullet will still be left in the cartridge case. This means that the case capacity is reduced quite a bit, which means you can’t fit as much powder in the brass as you would with other loads. This will result in a loss of velocity, which is not what you’re looking for if you want to go long range because the bullet needs to stay supersonic (some bullets can destabilize when they cross into the transonic barrier or into the subsonic barrier). So to combat this, the throat area (area before the lands) is extended so the bullet can stick further out of the case; resulting in full case capacity. So it sounds like a great solution right? Well the answer is . . . . . maybe.

    There are trade offs to long throating, which I’m just going to brush the surface on. Most bullets do not like to have a huge “jump” into the lands, although most bullets will tolerate small jumps into the lands. When a rifle is long throated and you shoot bullets that are lighter weight and not long, they may have a significant jump. The result is that many times, the lighter weight bullets will not shoot all that well in the rifle. So you have to choose to have full case capacity and maybe not have other bullets shoot well in the rifle, or you can lose some velocity and still maybe get away with shooting the VLD’s and standard bullets in the rifle. The other draw back that most people encounter has to do with the magazine length. Most of the time, VLD and long range bullets prefer to be seated “kissing” (touching) the lands; which is not how most other bullets shoot well. This means that if you have a long throated rifle and you load the bullet to kiss the lands, the cartridges start to have a pretty long over all length (OAL). Sometimes the length of these cartridges gets to be longer than the magazine length inside of the rifle. This means that you may have a repeater bolt action rifle, but if the cartridges are so long that they don’t fit in the magazine, you can only shoot the round that is chambered. So if the cartridges are longer than the magazine length, you have to single load every single round that you shoot (not preferable). So one has to “pick their poison” about whether you want to sacrifice some velocity, shooting normal chamber dimensions, and whether or not they have to single feed their rifle. MOST shooters will choose a kind of middle ground, they will throat their rifle long enough to have a bit more case capacity, but leave them short enough so that they will fit in the magazine. One should also always consider that later as you reload, you will need to chase the lands in order to maintain their accuracy with the VLD’s; so ideally you want to choose a length that leaves you a little “room to grow”.

    I mentioned earlier that we would talk about a consequence of not polishing the neck and throat area of the chamber; with the reason being that you do not want to get into the rifling. The consequence of not polishing this area is that there will be small burrs (sometimes microscopic) in the neck and throat area. Whether you realize it or not, these small burrs will shave a small amount of copper from the bullet until these burrs are finally removed. To make a long story short, the copper basically turns into a plasma because of the heat and pressure involved in firing a rifle, and settles in the rifling. This means that when you first break in a recently chambered barrel, there will usually be a fair bit of copper fouling; this will NOT be as common after the burrs are not present. This really does not impact the accuracy of the rifle over its lifetime as much as it does the copper fouling in the beginning of shooting the rifle. Copper fouling can take some time to remove, so some people prefer to “break a barrel in” and remove it gradually as it builds up; as opposed to letting a thick layer of copper build up that can be hard to remove. Some people would rather not deal with the break in process and just give it a long good cleaning later on after the burrs are worn off. One method is not necessarily better than another, just a preference, so there’s no point in getting into a huge debate about whether or not someone should break in a barrel. I will say it again, it will NOT have an overall impact in the accuracy or life of the barrel, but it WILL have an impact on how hard it is to remove the copper fouling from the barrel UNTIL the burrs from the neck and throat area are removed. It should be noted though that the fastest way to ruin a quality barrel is to OVER CLEAN, and IMPROPERLY clean (without a bore guide, from the muzzle, or both directions) a barrel. Most tactical rifle shooters believe that you should leave a barrel “fouled” (not cleaned to bare steel), so that your cold bore shots are more consistent. So the general rule of thumb amongst tactical rifle shooters is “shoot it for as long as it’s accurate, if your accuracy and consistency starts to drop, THEN clean it.” If you’re more interested in reason for barrel “break in” and some ideas of why to do it, you can find a good explanation from Krieger here. http://www.kriegerbarrels.com/Break_...246-wp2558.htm

    That concludes barrels and chamber modifications for the most part. If there are any questions on types of rifling, or anything I’ve been unclear on, please feel free to ask. Thanks for hanging in there, the brunt of all the modifications and common gunsmithing done to tactical rifles has been covered.

    Note: more mods like stocks, bedding, brakes, etc. will be added here and maybe more added later in the thread. This is related to space and I can only add 20,000 characters per post. LOL, yeah, it's a lot.
    Last edited by Tomcat088; November 4th, 2009 at 08:23 PM.

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    Default Re: Modifications for precision rifles

    Great post so far TC ... can't wait to read the rest.

    Got a feeling that this thread might become a sticky when it's done.
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    Default Re: Modifications for precision rifles

    Thank you very much Mojo, I'm glad that you, and hopefully some others will find the posts interesting and helpful. It's updated now with the bolt modifications, with barrels coming in the near future.

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    Default Re: Modifications for precision rifles

    Very nicely done Tomcat. Thanks for taking the time to pen such a thorough tutorial.

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    Default Re: Modifications for precision rifles

    Great info! I'll vote for sticky even though it's not done yet.
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    Default Re: Modifications for precision rifles

    Part 2 was done and somehow I missed it! Great job, keep up the good work!!!

    I will try and throw some thoughts together and get some questions up to feed this further.

    +1 for the sticky.

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    Default Re: Modifications for precision rifles

    More modifications have been added going over barrels and chamber modifications. Hope ya'll enjoy.

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