to crimp... or not to crimp... that is the question

C

condomboy

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just getting into the long range target game and going to reload my own to save money and hopefully gain some more reliability.

Looking at dies and some include a crimp die... should I... or should I not...? What has been the concensus for reliability / repeatability / accuracy? any impact by crimp?

will be running
.308WIN
Hornady Match cases
175gr A Max
IMR4064
CCI large rifle primers
 
From what I gather, crimping allows for more uniform discharge pressures - The bullet won't move until the pressure in the case overcomes the friction of the crimp, which will be a fair bit more than if it was just seated. If your crimps are uniform, along with your bullet and powder weights, you should expect consistent velocities and accuracy.

A lot of match shooters just measure their bullet seating so that the bullet is practically resting on the lands instead of being crimped. Provides the same effect with less manipulation of the brass.

I crimp because I do a lot of gopher shooting and having bullets fall out of or get pushed into their cases while in my pocket is annoying.
 
A resizing die squeezes the neck diameter smaller, the expander ball then makes the neck diameter larger. You can increase your neck tension by reducing the diameter of the expander ball just like a neck bushing die controls neck diameter and the cartridge would not require crimping. That being said the RCBS AR series dies have a taper crimp, "BUT" remember neck thickness, annealing (neck hardness) and trimming to the same case length effects the crimp pressure. So controlling neck tension during resizing would be more uniform.

Bottom line, I have two AR15 rifles and a bolt action .223, my AR15 carbine and SHTF ammunition is taper crimped, my AR15 A2 HBAR and bolt action ammunition is not crimped and a expander mandrel is used to expand the case necks to control neck tension and reduce runout.

Expander Mandrels and Neck Tension
http://www.accurateshooter.com/technical-articles/reloading/expander-mandrels-and-neck-tension/

Neck Tension — Not Just Bushing Size
http://www.accurateshooter.com/technical-articles/reloading/neck-tension-not-just-bushing-size/

Complete Precision Case Prep
http://www.accurateshooter.com/technical-articles/reloading/complete-precision-case-prep/

NOTE: AccurateShooter.com is a wealth of information on reloading and accuracy, and is a good place to spend some time reading and expanding your knowledge. You have the main webpage with articles and the reloading forum to expand your mind to bursting. :cheers:
 
Spawn-Inc said:
And while feeding in a semi and in lever guns.
Click to expand...

well in a lever gun, I didn't crimp .45/70 and ended up with a bullet pushed back from tension within the mag tube and didn't crimp firm enough on 500S&W and ended up having the recoil pull a bullet from the case

just haven't hand fed a bottle neck case before where those other factors I've experienced don't exist.
 
Target/precision loads = no crimp

Prep work and a good sizing die will give uniform neck tension. Crimping will take away from consistency.
I've got Redding bushing dies, and I'll put my Lee collet dies as a very close second, for consistent neck tension.

Have you already bought the Amax, cause there's better ;). They'll be good to learn with though.
 
9x19p said:
Target/precision loads = no crimp

Prep work and a good sizing die will give uniform neck tension. Crimping will take away from consistency.
I've got Redding bushing dies, and I'll put my Lee collet dies as a very close second, for consistent neck tension.

Have you already bought the Amax, cause there's better ;). They'll be good to learn with though.
Click to expand...

I have Lee dies on order and the A Max's are already on the bench waiting for the dies. What's better?
 
No crimp for target ammo. Crimping is detrimental to accuracy.
If your ammo falls apart in your pocket it's not loaded correctly.
 
condomboy said:
I have Lee dies on order and the A Max's are already on the bench waiting for the dies. What's better?
Click to expand...

Amax are a good bullet, I've sent many to 600 & 800, but there's always something better. I like Berger, so much that I'm a self proclaimed fan boy :). My best results were with VLD hybrids, 168gr specifically. I've never tried 175s.

Save the Amax for gongs, use true match bullets for groups.
 
There is no need to crimp for the .308 or any other centerfire rifle round for that matter, except if used in a tubular magazine lever gun. I used to load for a heavy recoiling .348 Win in a Win Model 71 and you sure needed to crimp for that one.

There is one use for a crimp in a .308 in though. I sometimes used to pull down 7.62 military ball ammo to make "Mexican match" ammo by re-seating a more accurate commercial bullet. In this case the Lee factory Crimp die was a good one to use. It is tolerant of varying case lengths.
 
bigedp51 said:
A resizing die squeezes the neck diameter smaller, the expander ball then makes the neck diameter larger. You can increase your neck tension by reducing the diameter of the expander ball just like a neck bushing die controls neck diameter and the cartridge would not require crimping. That being said the RCBS AR series dies have a taper crimp, "BUT" remember neck thickness, annealing (neck hardness) and trimming to the same case length effects the crimp pressure. So controlling neck tension during resizing would be more uniform.

Bottom line, I have two AR15 rifles and a bolt action .223, my AR15 carbine and SHTF ammunition is taper crimped, my AR15 A2 HBAR and bolt action ammunition is not crimped and a expander mandrel is used to expand the case necks to control neck tension and reduce runout.

Expander Mandrels and Neck Tension
http://www.accurateshooter.com/technical-articles/reloading/expander-mandrels-and-neck-tension/

Neck Tension — Not Just Bushing Size
http://www.accurateshooter.com/technical-articles/reloading/neck-tension-not-just-bushing-size/

Complete Precision Case Prep
http://www.accurateshooter.com/technical-articles/reloading/complete-precision-case-prep/

NOTE: AccurateShooter.com is a wealth of information on reloading and accuracy, and is a good place to spend some time reading and expanding your knowledge. You have the main webpage with articles and the reloading forum to expand your mind to bursting. :cheers:
Click to expand...

thanks for the links, give me something to read tonight :)
 
Yea I'll agree here, all the research I've done and my own experience, crimping when you want accuracy isn't the best idea. My velocity spread was much worse when crimping.

Second vote for Berger bullets here to. Their support guy (Bob) is awesome. He has put up with my incessant questioning for a while!
 
Most reloaders will tell you not to crimp as it is detrimental to accuracy.

Having said that, can anyone tell me why Swiss GP11 Military ammo is so incredibly accurate? It is a FMJ-BT projectile with callelure and it has a substantial crimp.

I have been reliably informed that the Swiss use standard issue military cartridges in international rifle matches - no Match ammo needed nor required...
 
Another thing to remember is not all target bullets have a cannelure or crimping groove. Looking through Hornadys catalog AMAX do not have a crimping groove, trying to crimp a bullet without this feature is not recomended by bullet manufactures.
 
Every time I read one of these crimp/no crimp threads I read the same B.S. About "if you crimp a match bullet your ####'l fall off" or "if you crimp your accuracy will fall into the toilet".
All I'll say is this: stop reading this and go and try it - you may just be surprised with where the experiment takes you.

I've loaded crimped match ammo that has shot very well indeed, and in some cases superior to non-crimped stuff.
Here is a good photo of a crimped .223 (77smk) with two pulled bullets - one crimped, the other not. The crimping makes less indentation than the rifling.

 
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