chrono, do I need one?

[vapochilled]

Just starting out in reloading, and am wondering if I "need" a chrony? Most load data gives MV data, so all I'd be doing is confirming that which is known, however on the flip side, it would offer peace of mind that was not running too hot.
Is a chrony a staple tool for reloaders or a luxury item?

[max384]

Just starting out, I'd say it's not needed. Over time, once you start fine tuning your loads and your reloading procedure, you're gonna want one. I reloaded for quite some time before I had some extra cash and bought one. That said, once I bought it, I don't know how I got along without it for determining the best loads for a particular round. If you're cash strapped (as many are after taking the plunge into reloading), I'd say skip it for now. If you've got the extra money, get it.

EDIT: The Chrony won't tell you that you're running too hot. There are way too many variables that affect velocity for a high velocity to confirm that you're too hot. Conversely, you may be loading too hot, but your bullet velocity may be right on target. The most prominent variable is barrel length. Your load book will only use one barrel for testing. If the barrel that you use is different from their test barrel, your velocity will also be different.

Your fired cases will tell you whether or not you're loading too hot.

[Flash]

Your fired cases will tell you whether or not you're loading too hot.

Eggggzactly! Learn to read the primers, and you'll be alright.

Flash

[vapochilled]

Eggggzactly! Learn to read the primers, and you'll be alright.

Flash

Care to expand on that a little?

[Lycanthrope]

Care to expand on that a little?

As pressure increases primers will start to flatten. At that point, in most guns, you are pushing the limit (generally speaking).

Go far enough and you can actually have the primer flow back into the breachface. Please don't TRY to do that.

So.....if primers aren't going flat you're ok in most modern firearms.

There are, however, some exceptions..... like the K31 where the case is not fully supported and you can have issues with hotter loads that would be safe in most bolt rifles.

Lycanoversimplifiedthrope

[vapochilled]

As pressure increases primers will start to flatten. At that point, in most guns, you are pushing the limit (generally speaking).

Go far enough and you can actually have the primer flow back into the breachface. Please don't TRY to do that.

So.....if primers aren't going flat you're ok in most modern firearms.

There are, however, some exceptions..... like the K31 where the case is not fully supported and you can have issues with hotter loads that would be safe in most bolt rifles.

Lycanoversimplifiedthrope

Makes sense, but does the back face/primer touch the back of the breach anyway? if it did not not, surely the case would move back as it fired, robbing the bullet of "some" energy?
Or are you referring to the primer actually flattening against this face? Again, makes sense.

So if the the load is correct, the primer should not move at all I assume as the flash hole and therefore the pressure rise in relation to the "open" barrel is (should be) low, all the energy going forward.
Ok, that raises another Q for me, if the bullet is seated too deep in the case, you could see primer deformation and assume the load is too hot when in fact the cause is bullet seat depth?
I see this is going to be a fun learning curve

[justashooter]

depends on what you are reloading.

"reading primers" is crap. too many variables in primers for this trick to be reliable.

chronographs are valuable tools and reasonably cheap. if you are reloading moderate velocity pistol rounds in most cartridges you don't need one. if you are reloading exotic cartridges (or using standards in special crcumstances)you should have one.

case in point, you are reloading for a trapdoor springfeld, have collected lots of data fom the interwebs and several good books, but are concerned about your face.

case in point, you want to duplicate a standard velocity load for said trapdoor so that the ladder sights will be reasonably well calibrated at 1000 yards.

case in point, you are reloading 270 win for your winny 54 and are using powder your grandfather bought in 1978 (has the powder become sensitized?).

case in point, you are reloading for bowling pin matches and want to know your velocity to determine whether you are major or minor power factor.

[red dog]

nice thing about a chrony you have a reliable way of checking your overall consistency of your reloads, as in close fps numbers. close numbers equate to tight groups barring shooter error.

[max384]

Makes sense, but does the back face/primer touch the back of the breach anyway? if it did not not, surely the case would move back as it fired, robbing the bullet of "some" energy?
Or are you referring to the primer actually flattening against this face? Again, makes sense.

So if the the load is correct, the primer should not move at all I assume as the flash hole and therefore the pressure rise in relation to the "open" barrel is (should be) low, all the energy going forward.
Ok, that raises another Q for me, if the bullet is seated too deep in the case, you could see primer deformation and assume the load is too hot when in fact the cause is bullet seat depth?
I see this is going to be a fun learning curve

When a round is fired, the firing pin strikes the primer. If the round is not already against the headspace stop point (I know there's a better name for this, but I'm not thinking of it right now), it will be pushed there. The primer will detonate and ignite the powder. During this process, the primer will unseat and be pushed back against the breach face. The burning powder will then build up pressure and propel the bullet into the barrel, while at the same time the pressure is pushing the case back against the breach face and reseating the primer. This happens normally. The primers flatten when this process happens with more force because of higher pressures. This also illustrates one of the reasons why headspace is so important.

One thing to note, however, is that primers can flatten and still be within safe pressure limits, particularly on high pressure cartridges. That is yet another reason everyone recommends to start at the lower loads and work your way up. This way you can watch the progression of the primers as you work the load up.

You are correct that seating the bullet too deeply can result in primer flattening. Seating the bullet too deeply will increase pressures. The flattened primers are a measure of pressure, not how much powder a case contains. A case with the proper powder and a bullet seated too deeply or a cartridge with too much powder are both hot rounds. Make sure you get the correct load data for the bullets you are using, to include proper OAL. For example, if you're loading round point bullets, make sure you're not using the listed OAL for a flat nose bullet. Make sure that you are also accurately measuring the OAL of each round until you get very familiar with the process. Then, you can find your own procedure for measuring (some do every round, some every 10th, some every 100th, etc.).

[L T C]

If nothing else, you will know exactly what "your" reloads are doing. Peace of mind.

Published data test results usually are done with a gun or test barrel that is not what you are using.

I don't load any wild or exotic loads but I find the chrono results worthwhile. I know exactly what my stuff is doing out of my stuff.

I'd say get one if you get the chance. I've got the Competition Electronics ProChrono Digital and it works very well. Hasn't missed a shot, using it outdoors in all kinds of light.