Home Forums Reloading Big Game Rifles does crimping really help?

I've been reading on the reloading forums quite a bit lately about crimping high powered rifle cartridges. My question is, has anyone done any investigation if crimping improves accuracy? People on one forum claims crimping does inprove accuracy, while others on the same forum say it makes no difference, that crimping is done only to keep bullets from pushing in on lever-action rifles. Also, does crimping increase pressures? Well, I guess that is enough damage for one session. Thank you ... Tom Purdom

It adds one more variable to the mix, do you need that?

One time for grins, I worked up loads that were crimped (Hornady 139gr SP) in my 7mm-08. Once I found a good load, I switched to loading without crimps. No difference in accuracy and little fps difference over the chrono. I think the fps difference was due to temperature.

Certainly not scientific but that is my experience.

RH

Though I've heard crimping can make ammunition more accurate, I have never found that to be the case. The only reason I ever crimp is to keep bullets in a magazine or revolver cylinder from moving under recoil.

I once loaded up some Barnes Triple Shock X Bullets and, for whatever reason, they were so loose in the cartridge that I could easily turn them by hand. I shot 3 of these and three cartridges with tight bullets into a 100 yard target and the group with the loose bullets was significantly smaller.

I also shot with a guy in bench rest matches who was much better than I. He would reload the same 5 cartridges at the range between 5 shot strings. He would dump the powder in and then set the bullets in by hand without a press (i.e., they were loose). He got 1 hole groups at 100 yards.

dont do it

I have tried it enough to give you a definite maybe. <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />

I found one load in one rifle (7.62 X 39 ) where it made a measureable difference to crimp. On the order of an inch group size better by crimping.

BCR

If you are talking about crimping with the Lee Factory Crimp Die, then maybe. If you are talking about the roll crimp that comes with the seating die, then I duno, I will not crimp with my seating dies. Here is some interesting reading on the effects of the Lee Factory Crimp Die and accuracy.
http://www.accuratereloading.com/crimping.html

Well, most factory cartridges are crimped, and most factory cartridges are pretty damned accurate. They load a bazillion times more ammo than we do, and I'd have to say that just maybe they've learned something. It would certainly be less expensive for them to eliminate the crimp, but they still do it - so they MUST think there's a good reason for it.

I've convinced myself that a crimp does make a notable improvement in accuracy when used on very small cartridges like the Hornet, Bee and Fireball. The reasons have to do with primer impulse, light bullets and low neck tension. All three combine to change the consistency of ignition, bullet obturation, land engraving and pressure rise. But in larger cartridges, those effects diminish greatly.

I did some timkering around with a .223 bushmaster. I found I had to reduce th load 1 gr when I crimped.I f I ddidn't crimp, that brass was so thin at the necks that a lot of times the bullets would telescope back into the case. I also fooled around with 7 x57 and saw no decernable differnce. Bench resters are a whole differnt breed though

That is pretty much what I found on the medium to 35 bore centerfires. If a good load already, very little noticeable change, if any.

On bore sizes 6mm down, there seems to be a tendency to improve velocity SD, and grouping, sometimes dramtically. Have also found on the smaller bores, that ten shots groups are the easiest to see this effect, without letting barrel cool down. One exception: I've never seen this difference with .223, that was VISIBLE, and have no idea why.

I do think Rocky nailed it on the hornet thread when he mentioned the bullet jump to the throat issue. When you have thin walled necks, and factory spec throats, think it only makes sense to obdurate the base as quick as you can, or at least getting it starting to obdurate

One way to see this, is in revolvers. Shooting for accuracy with your best load; then try a group with that exact same load, only not crimped. Single shot the revolver on same cylinder hole, and check for bore obstruction (might stick a bullet, be safe).

There is SOMETHING definitely happening with a crimp. May or not be necessary, in some situations, so just have to try it to view results.

If you have heavy bullets and lots of recoil you will be forced to crimp, just to keep the bullets from sliding back into the cases. In revolvers it is a must. In rifles with light bullets or for benchrest shooters who load one round at a time it would be unneeded. Try a light crimp if you think you need it.
Otherwise I would try and live without it.
whelennut

+1

I do crimp my 30-30 and 22 Hornet loads.
Don't crimp anything else.

Don

In hunting loads, with certain combinations of components, crimpimg can improve accuracy, it can also have little effect or be detrimental. If I'm working with a certain powder (that I like for example because it gives good velocity and meters well: like 4320, etc) I may try loads both ways to see if crimping will help. I know that exact powder responds well to crimping with heavy bullet loads in 223.

I often use at least light crimps on my hunting loads just to prevent bullet movement with ammo that may not be treated like target ammo. It sure beats the occasional pocketful of powder granules I have experienced a few times.

50gr. V-Max's shoot well with just the slightest crimp out of my BM Varminter.

I crimp all my hunting loads with the factory crimp die. I can't tell any difference in accuracy, I crimp because I've noticed that the bullets will set back in the case under recoil in any uncrimped round that's in the magazine of a bolt action. Even my 257 Roberts will set the bullets back under recoil.

I use the lee die for every caliber that i can get one for. Had trouble with a 300 winnie once and don't want it again.

I don�t recall a factory load that wasn�t crimped. I�m sure they do it for reasons other than accuracy, but they wouldn�t do it if it created inaccuracy.

Factory loads are crimped into a cannelure groove. The same bullets, available for handloading, often do not have the groove.

So, far, I only crimp when the bullets have the crimping groove, and it�s in the right place for the OAL I want to use, or need to use.

I thought that was what was recommended. Some of you guys seem to be saying, you crimp even without the crimping, (cannelure) groove. Is that what you�re doing? Is that what you mean by a �light crimp�? Not enough to damage a bullet without the crimp groove?

Thanks
Smitty of the North

When I crimp I use the Lee Factory Crimp Die. It does not need a cannelure to work. You can crimp bullets with or without a cannelure.

http://www.leeprecision.com/cgi/catalog/browse.cgi?1165157837.3602=/html/catalog/dies-crimp.html

exactly, and it looks just like the factory crimps.

When you buy Winchester component bullets, sometimes they have cannelures, sometimes they don't. I prefer the ones sans cannelures and crimp with a Lee FC die to get sub MOA groups with my chosen load. Not crimping opens those groups some and crimping on even the plain jacket seems to affect the bullet less the the rolled cannelure does.

Crimping does add another variable as "Furprick" asserts, it can also eliminate several which can be a pretty good trade-off.