What are the benefits

[tigertom65]

What are the benefits of a 20" barrel .308, a 22" barrel .308, and a 24" barrel .308 when hunting? I understand there will be a small weight difference but I want to know more about accuracy related differences.

I just want to know that if I drop down to a 20" barrel I will still be accurate out to 500 yards? I probably won't shoot at anything past the 300 yard mark, but who knows someday I might. This rifle will be used for hunting and possible target fun. It will not be used for target shooting in contests.

Why are some 308s a 1:10" twist while others are a 1:12" or a 1:9 7/8"??

If I went to a 20" barrel what should the twist be for an accurate gun?
What about the 22" barrel?

The X-Bolt Hunter and Stalker have 22" barrels but the micro hunter has a 20" barrel, and some varmint rifles have a 24" or a 26 " barrel. Will the X-bolts still be accurate to at least 300 yards with the 20" barrel? What about at 500 yards?

[Decholder]

Longer barrels can help improve accuracy because it allows more for more pressure to build behind the bullet thus having a higher muzzle velocity, which equals your bullet going downrange faster and giving wind and gravity less time to act on it. But because of the extra length of the barrel, that means that any movement of the gun while the bullet is still going down the barrel may also have a negative impact on bullet placement. In short, yes, a longer barrel will aid accuracy of the rifle, but the differences will be fairly negligible.

The optimum twist rate for .308 is the 1/12 rate. http://www.snipercountry.com/hottips/TwistRate.htm

Gunsmiths generally use the Greenhill Formula to determine the optimal twist for a given bullet. The formula is T=150(d/r) for velocities from about 1500 to 2800 fps. Substitute 180 for the 150 value for velocities exceeding 2800 fps. "T" is the twist rate. "d" is the bullet diameter. "r" is the bullet length to diameter ratio (length of bullet divided by diameter). In .308, it works out fairly well. Sierra 168 grain Matchking is 0.308 inches in diameter. Bullet length is about 1.210 inches so we have a length to diameter ratio of 3.929. Plugging this value into the formula and using the 150 constant (the proven best velocity for the 168 grain MK is 2550 - 2600 fps), we get T=150 x (.308/3.929); T=150 x 0.078; T=11.76 inches or 11 3/4 inch twist

So I'd opt for the 20 inch barrel with the 1/12 twist rate.
Hope this helps

EDIT: By the way, a good quality rifle will be the major factor in what determines at what range a rifle will still be acceptably accurate. I have no experience with the x-bolt, but Army M24's (Rem 700) are "technically" good out to about 800m.

[Posit]

Understand your question is far more complex than you probably realize.

Twist rate correlates to the length (and therefore weight) of the bullet which can be stabilized when fired thru a rifle barrel. Heavier ball requires a faster twist rate to stabilize. Thus, a 1-10 twist will stabilize a heavier ball than a 1-12 twist, and would be more suited for longer rainge shooting... in a .308, this would probably be important at/above 800 yards.

For your stated purpose, either will suit, but other factors are much more important than twist rate. How the gun feels, how it comes up, how comfortable it is at the shoulder, trigger pull, optics, specific bullet you select, etc etc will have much more impact on how well you and the rifle shoot. If you buy a quality rifle, the typical manufacturer's twist will do what you want. That said, get a good rifle, 20", 22" or 24" barrel, put a good scope on it and have fun.

[tigertom65]

If I use the example given about the Greenhill fomula then a 20" barrel or a
22" barrel with a 1:12 twist will fire the same 168 grain bullet accurately but the 22" barrel will fire it faster right?

Will the X-Bolt with its 1:12 twist fire a 180 grain bullet accurately or not? Is a 168 or 150 grain bullet suitable for use in Whitetail or black bear hunting using commercial ammo (Not reloads)?

It looks like the 22" barrel is good in the Browning but in the Remington or Savage the barrels are 1:10 so they should technically fire even more accurately (Than the Browning) using the larger grain bulllets right?

If I don't need anything more than a 168 gr or 150 gr bullet I should be ok with the Browning. I think.

[Decholder]

If I use the example given about the Greenhill fomula then a 20" barrel or a
22" barrel with a 1:12 twist will fire the same 168 grain bullet accurately but the 22" barrel will fire it faster right?

Right.

Will the X-Bolt with its 1:12 twist fire a 180 grain bullet accurately or not? Is a 168 or 150 grain bullet suitable for use in Whitetail or black bear hunting using commercial ammo (Not reloads)?

I have no experience with the x-bolt, but if it is a quality rifle, then you should be good to go. And as for the bullet weights, I don't think you should have an issue with the lighter weights...as long as they make up for it in velocity. In fact some 150g bullets retain more energy past 100m than 180g bullets, do to the extra velocity of the round.

It looks like the 22" barrel is good in the Browning but in the Remington or Savage the barrels are 1:10 so they should technically fire even more accurately (Than the Browning) using the larger grain bulllets right?

Bullet weight does not play a significant factor into determining proper twist rate, but generally heavier bullets will also be longer, therefore making them better suited to lower twist rates. The optimum length of a bullet of .308 caliber being used in a 1/10 barrel would be 1.42in. I personally would stick with the 1/12, it is a good compromise if you will be firing varying bullet lengths.

If I don't need anything more than a 168 gr or 150 gr bullet I should be ok with the Browning. I think.

Sounds like a plan, good luck!

[Xringshooter]

Whitetail and bear in PA will be very easily be taken with 150-168 grain bullets. These bullet weights are going to be good for longer range shots also.

[Tomcat088]

Longer barrels can help improve accuracy because it allows more for more pressure to build behind the bullet thus having a higher muzzle velocity, which equals your bullet going downrange faster and giving wind and gravity less time to act on it. But because of the extra length of the barrel, that means that any movement of the gun while the bullet is still going down the barrel may also have a negative impact on bullet placement. In short, yes, a longer barrel will aid accuracy of the rifle, but the differences will be fairly negligible.

The optimum twist rate for .308 is the 1/12 rate. http://www.snipercountry.com/hottips/TwistRate.htm

So I'd opt for the 20 inch barrel with the 1/12 twist rate.
Hope this helps

EDIT: By the way, a good quality rifle will be the major factor in what determines at what range a rifle will still be acceptably accurate. I have no experience with the x-bolt, but Army M24's (Rem 700) are "technically" good out to about 800m.

There is a lot of debate about whether a long barrel has more inherent accuracy than a shorter barrel. First off, although velocity can help with inherent accuracy, it is NOT the most important aspect of accuracy. Everything that you've said so far is true about time of flight, wind drift, etc.; which bullet weight in that time of flight and wind conditions will also effect what you're speaking of. Velocity is important, but CONSISTENCY is king. If you know very much about precision shooting, then you know that the "hottest" load in a rifle isn't usually the most accurate. The most accurate load is the one that is most consistent. I'd much rather have single digit stand deviations in velocity on the chronograph, rather than the highest number on the chronograph.

You mention barrel length and how movement can have an affect on the bullet, you forget some things. You don't even mention the effect of angles that come in to play with longer/shorter barrels. When you move a "longer lever" the same distance as a shorter lever (with the fulcrom being the rest); the longer barrel actually travels a greater distance on the other side. This means if you move the stock of the rifle the same distance as you would a shorter barrel, you'll actually miss the shot by a larger margin of error because the angle that the end of the barrel moved was MORE than the shorter barrel. There are lots of things to consider, and from the way that you have presented them; it's much too simplified. Longer barrels do NOT necessarily aid in accuracy, it's kind of up in the air, and a matter of opinions. Many times, which rifle will be better is much more dependent on other factors and what type of shooting someone will be doing. Bullet weight, and the velocity that you require is important (it's different for different applications); although it is more difficult to push the 20" barrels past 800 yards, especially if you're not using reloads.

Either way, by making statements like 1/12 twist rate is optimal for .308, you show your inexperience to the more experienced shooters. I hate when misinformation is presented to people seeking advice like it's fact.

. . .
Bullet weight does not play a significant factor into determining proper twist rate, but generally heavier bullets will also be longer, therefore making them better suited to lower twist rates. The optimum length of a bullet of .308 caliber being used in a 1/10 barrel would be 1.42in. I personally would stick with the 1/12, it is a good compromise if you will be firing varying bullet lengths.

Sounds like a plan, good luck!

Bullet weight and length, and LOTS of other factors play into optimum twist rate. Generally heavier bullets are longer, but this isn't always the case. You ever shot steel core ammunition? How about ammunition with tungsten cores? Their weights are rather heavy for their bearing lenght. If you are merely going by what you state about their length, you're not going to have enough twist rate to stabilize them. The fact of the matter is that the length of the bullet and the weight of it all contribute to the twist rate that it needs to be stabilized.

You again state silly facts like "the optimum twist rate for a .308 caliber being used in a 1/10 twist barrel would be 1.42". Have you ever truly studied stabilization? You don't even mention under what temperature, barometric pressure, altitude, or velocities that the bullet is being driven in. You ever shot subsonics? They're a different game as well. The people that generally are speaking in terms of what you're talking about will usually talk about lengths of bullets in terms of "caliber lengths" (as a ratio). I think you're getting a bit past your experience level with some of the comments that you're making. I'm not trying to be a jerk, but I don't want someone asking questions that relate to a purchase, to be misinformed.

Edit: P.S. I hope that you realize that a 1 in 10 twist is FASTER, than a 1 in 12 twist. You mentioned that heavier bullets are better suited to lower twist rates, which is exactly the opposite of the truth. 1:10 is FASTER than 1:12.

[Tomcat088]

Ok, now that I've got that out of the way, this post is for you Tigertom, and hopefully it will help you a bit more. There have been quite a few questions asked about velocity, barrel length and .308 twist rates. Here is a pretty recent thread where I talk some about twist rates and some about bullet weights. I also link to some other threads that might have some information that might help you out. http://forum.pafoa.org/rifles-42/540...questions.html .

I cover in quite a bit of depth a question about barrel length and velocity in this thread, that you may find interesting. It may also help in your decision in terms of application http://forum.pafoa.org/rifles-42/422...-tactical.html .

If I was going to kind of summarize everything and give you a personal response, it would go something like this. For your type of shooting a 20" barrel will be MORE than sufficient, and will shoot EVERY BIT as accurately as even a 26" barreled rifle. It will handle MUCH better. I kind of sounded like a defended shorter barrels in my last post, although for MY applications, longer barrels usually work better. The barrel that I put on my recent custom build was 26" long. I hope that tells you that I'm not trying to tell you what I like, but give you an honest assessment of what I think will work best for YOU.

You will NOT see any significant difference in velocity or accuracy, between a 20" and a 22" barrel. Both of those rifles will shoot out to 800 yards accuratly without any problems, although both of those choices would have more drop than say a 26" rifle. The twist rates are for different bullet weights and it will help you find the bullet that will most likely shoot best in your rifle. If you read some of the other posts that I linked to, you'll see that it's honestly kind of a complicated thing to determine with multiple variables.

At .308 velocities, you will be fine with a 1:12 twist rate for practically anything that you'd want to shoot. You would be able to stabilize the heaviest of bullets with the 1:10, but it's probably not what you're going to be shooting. As Xringshooter said, you will be FINE with anything between 155 grain bullet to 180 grain bullet in your .308. Most peopel consider even a 180 grain bullet a little heavy on deer, but it's my preferred load on deer actually. It's all up to you and your rifle. The heavier bullets will have a bit more drop at extended ranges, although they will carry MORE kinetic energy to the extended ranges. The lighter bullets will start out fast and have less drop (and recoil), but won't carry their kinetic energy as far as the heavier bullets. BOTH of those bullet weights will be VERY lethal past 500 yards (which you mention), and so you have NO worries. Typically from the shorter barrels, it's easier to get good velocity, and accuracy with the lighter weight bullets; they WILL get the job done. Just make sure that you use a hunting bullet (not a match grade bullet), and place it where it's supposed to be. It doesn't matter if it's a Hornady Interbond or SST, Nosler accubond/ballistic tip, Sierra GameKing, Bear claws, Barnes XTP, etc, etc, etc. There are TONS of choices of quality game bullets for the .30 calibers, so just pick one that shoots well in your rifle and that you can deal with, and you'll be good to go.

Remember that almost every modern hunting firearm is very accurate and you won't have any problems hitting animals at 300 yards. The shooter is a MUCH more limiting factor than the rifle is. If you have any questions about bullets, twist rates, or anything else, I'll be happy to answer them in PM's, or in this thread. Hope that helps and best of luck to you.

[Decholder]

There is a lot of debate about whether a long barrel has more inherent accuracy than a shorter barrel. First off, although velocity can help with inherent accuracy, it is NOT the most important aspect of accuracy. Everything that you've said so far is true about time of flight, wind drift, etc.; which bullet weight in that time of flight and wind conditions will also effect what you're speaking of. Velocity is important, but CONSISTENCY is king. If you know very much about precision shooting, then you know that the "hottest" load in a rifle isn't usually the most accurate. The most accurate load is the one that is most consistent. I'd much rather have single digit stand deviations in velocity on the chronograph, rather than the highest number on the chronograph.

I never said that velocity was the most important aspect of accuracy, and I agree with you that consistency is far more important. But as the question was about barrel length's affect on accuracy, it does impact velocity and can improve your shot provided other factors are consistent.

You mention barrel length and how movement can have an affect on the bullet, you forget some things. You don't even mention the effect of angles that come in to play with longer/shorter barrels. When you move a "longer lever" the same distance as a shorter lever (with the fulcrom being the rest); the longer barrel actually travels a greater distance on the other side. This means if you move the stock of the rifle the same distance as you would a shorter barrel, you'll actually miss the shot by a larger margin of error because the angle that the end of the barrel moved was MORE than the shorter barrel.

That's exactly what I was getting at. I didn't "forget" about anything, I simply didn't state the mechanics of the situation.

There are lots of things to consider, and from the way that you have presented them; it's much too simplified. Longer barrels do NOT necessarily aid in accuracy, it's kind of up in the air, and a matter of opinions. Many times, which rifle will be better is much more dependent on other factors and what type of shooting someone will be doing. Bullet weight, and the velocity that you require is important (it's different for different applications); although it is more difficult to push the 20" barrels past 800 yards, especially if you're not using reloads.

Either way, by making statements like 1/12 twist rate is optimal for .308, you show your inexperience to the more experienced shooters. I hate when misinformation is presented to people seeking advice like it's fact.

Ok, after looking at my post again, I concede on this point, it did sound like I was stating that 1/12 was flat out the best for all .308 bullets, that was my opinion on what I (and others like me) prefer. I should have stated that a 1/12 twist rate is the optimum for what I use, and is similar to what the Army uses, and I like the fact that it provides a good middle ground if you are going to be shooting varying lengths/weights of ammo. The other twist rates have their niches as well.

Bullet weight and length, and LOTS of other factors play into optimum twist rate. Generally heavier bullets are longer, but this isn't always the case. You ever shot steel core ammunition? How about ammunition with tungsten cores? Their weights are rather heavy for their bearing lenght. If you are merely going by what you state about their length, you're not going to have enough twist rate to stabilize them. The fact of the matter is that the length of the bullet and the weight of it all contribute to the twist rate that it needs to be stabilized.

Yes, I have fired bullets with different cores, and yes it plays a factor in proper twist rate (the second half of the Greenhill formula). I was using calculations for lead core bullets, seeing as you don't hunt deer or bear with tungsten cores, unless of course your game just happens to be wearing body armor.

You again state silly facts like "the optimum twist rate for a .308 caliber being used in a 1/10 twist barrel would be 1.42". Have you ever truly studied stabilization? You don't even mention under what temperature, barometric pressure, altitude, or velocities that the bullet is being driven in. You ever shot subsonics? They're a different game as well. The people that generally are speaking in terms of what you're talking about will usually talk about lengths of bullets in terms of "caliber lengths" (as a ratio). I think you're getting a bit past your experience level with some of the comments that you're making. I'm not trying to be a jerk, but I don't want someone asking questions that relate to a purchase, to be misinformed.

I stated that the optimum length of a .308 bullet being used in a 1/10 barrel was 1.42" using the greenhill formula, the most widely accepted rule of thumb to base these calculations on. And yes, I have studied stabilization, but since the question was about twist rates and barrel lengths, I tried to keep it simple and didn't feel the need to implicate the ballistic coefficient and all the other environmental factors that come into play for a long range shot. And no worries, I don't think you're a jerk

Edit: P.S. I hope that you realize that a 1 in 10 twist is FASTER, than a 1 in 12 twist. You mentioned that heavier bullets are better suited to lower twist rates, which is exactly the opposite of the truth. 1:10 is FASTER than 1:12.

Yep, I goofed on that one.
Hope that clears things up a little.