Taper Crimp vs Factory Crimp

[markm]

Bolt gun or AR? All looks both pretty good and comparable to me.

This was the Geissele super duty. It has a much nicer scope than the Bolt gun. I agree that they're fairly comparable with the Taper flyer being the only area of concern because I don't think I pulled that shot. I'll probably repeat the test some more to decide what seems best.

[1168]

This was the Geissele super duty. It has a much nicer scope than the Bolt gun. I agree that they're fairly comparable with the Taper flyer being the only area of concern because I don't think I pulled that shot. I'll probably repeat the test some more to decide what seems best.

I’m looking forward to reading about it.

[Molon]

For hand-loads that are capable of producing statistically significant sub-MOA precision when fired from an AR-15 that has a match-grade barrel, crimping the case-mouth/bullet will degrade precision. The graphic below shows the results of three 10-shot groups fired in a row using hand-loads topped with the 77 grain Nosler Custom Competition bullet (along with MK262 Mod 1 for comparison.)




....

[markm]

That fairly closely mirrors the 69gr RMR test in this thread. But the variable that the crimp theoretically helps with is inconsistent neck hardness from non-annealed case mouths. I say theoretically because it's difficult to prove.

In a perfect world.. if I weren't loading hundreds of OTMs per week, and only fired 20 or so really good loads... I'd figure out an annealing process and strive to eliminate the Lee FCD.

So the Factory Crimp Die is a work around to improve accuracy with mixed brass of varying case mouth/neck hardness so that higher volumes of ammo can be made. Prior testing (4-5 years ago) showed significant accuracy loss without the FCD with 77s. I may retry that again since the 69gr test showed some promise with un-crimped ammo.

[MegademiC]

That fairly closely mirrors the 69gr RMR test in this thread. But the variable that the crimp theoretically helps with is inconsistent neck hardness from non-annealed case mouths. I say theoretically because it's difficult to prove.

In a perfect world.. if I weren't loading hundreds of OTMs per week, and only fired 20 or so really good loads... I'd figure out an annealing process and strive to eliminate the Lee FCD.

So the Factory Crimp Die is a work around to improve accuracy with mixed brass of varying case mouth/neck hardness so that higher volumes of ammo can be made. Prior testing (4-5 years ago) showed significant accuracy loss without the FCD with 77s. I may retry that again since the 69gr test showed some promise with un-crimped ammo.

This discussion coupled with the primer pressure-wave thread makes me wonder if powder choice is a relevent variable.

Molon, what powder are you using?

Once I tighten up some other stuff on my end, I'll try an experiment as well. I need to find better primers first!

Side note: how important is neck expansion with bthp brass jackets? I can feed them rmr bullets with no expansion, which i assume is due to the brass jacket being slightly harder than pure copper (nossler cc would get material scraped off).

[czgunner]

For hand-loads that are capable of producing statistically significant sub-MOA precision when fired from an AR-15 that has a match-grade barrel, crimping the case-mouth/bullet will degrade precision. The graphic below shows the results of three 10-shot groups fired in a row using hand-loads topped with the 77 grain Nosler Custom Competition bullet (along with MK262 Mod 1 for comparison.)




....

Great info, as usual.
I seem to remember hearing that a FCD improves accuracy. Interesting, I think this is is first time I've seen data that proves what it does.

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[grizzman]

I agree that comparing handloading with cases fired multiple times (and with different numbers of times fired) to new production ammo isn't completely apples to apples.

I always apply a light crimp to improve consistency, and have had great results.

[markm]

This discussion coupled with the primer pressure-wave thread makes me wonder if powder choice is a relevent variable.

Has to be. Different bulk densities and burn rates have to play a role. You know? Those psycho friggin CCI 41 primers might pair up well with Varget (stray thought) due to it's relatively slower powder burn rate.

I agree that comparing handloading with cases fired multiple times (and with different numbers of times fired) to new production ammo isn't completely apples to apples.

I always apply a light crimp to improve consistency, and have had great results.

Even when I loaded same batch LaPua in .308, I would get wildly different neck tension in the same 50 round box all fired together. That's when I started annealing large caliber. I just can't do it on .223 due to volume.

[Krazykarl]

To crimp or not to crimp...
1. Bolt action = no crimp
2. Semiautomatic = crimp

There is a point where the compromise between reliability and consistent precision lies. In the slam bam world of a push feed semiautomatic rifle, how much neck tension can reliably hold a bullet without a crimp?

[markm]

To crimp or not to crimp...
1. Bolt action = no crimp
2. Semiautomatic = crimp

There is a point where the compromise between reliability and consistent precision lies. In the slam bam world of a push feed semiautomatic rifle, how much neck tension can reliably hold a bullet without a crimp?

I don't crimp .308 gas gun ammo and that doesn't seem to be any issue.. And my neck tension is pretty good on the seating die before crimp. I could totally go No Crimp if that was what yielded the best results.