Lee factory crimp die

[Rich Coyle]

Gentlemen,

Butterbean suggested a Lee factory crimp die for dialing a load. On my first try I gave it about half a turn after touching the case mouth. Obviously that was too much. The next one was 1/8 turn and the next one was 1/16 of a turn after touching the case mouth. I guess I should have started with the small increment in the first place. (That's what he suggested.) The load is 7mm Hammer Hunter 90 grain bullet with the crimp in the top "groove". The powder is IMR7828 @ 99.0 grains. The primer used is a Winchester WLRM. The first group measures 2 3/8". The next is 1 1/4" while the last one measures 5/8".

Visually I could not tell anything happened on the 1/8 turn and the 1/16 turn. But most certainly something is going on.

 

[K.E.C. Darkside]

Did I miss what cartridge, 7mm.
Impressive F.P.S.

 

[Rich Coyle]

I being the genius I am, I forgot to mention the case. It is a 7-.338 RUM using 7 RUM or .300 RUM brass so I get an extra .100" longer neck. The jump for the bullet to the lands must be an 1/8" or more since it is so short.

 

[Bob Wright]

Good model for you. Maybe 1/16 is enough. It's just a slight crimp, but the data is there.

 

[Pdvdh]

Lee Factory Crimp Die = Magic with some loads. And it rarely hurts precision. Generally improves it.

 

[ButterBean]

Gentlemen,

Butterbean suggested a Lee factory crimp die for dialing a load. On my first try I gave it about half a turn after touching the case mouth. Obviously that was too much. The next one was 1/8 turn and the next one was 1/16 of a turn after touching the case mouth. I guess I should have started with the small increment in the first place. (That's what he suggested.) The load is 7mm Hammer Hunter 90 grain bullet with the crimp in the top "groove". The powder is IMR7828 @ 99.0 grains. The primer used is a Winchester WLRM. The first group measures 2 3/8". The next is 1 1/4" while the last one measures 5/8".

Visually I could not tell anything happened on the 1/8 turn and the 1/16 turn. But most certainly something is going on.


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It's crimping whether you can see it or not, awesome trigger work

 

[ButterBean]

Lee Factory Crimp Die = Magic with some loads. And it rarely hurts precision. Generally improves it.

I've never seen it " Hurt" a load

 

[Outdrmn]

I have found Butter Bean's advice on crimping very helpful. My 300wm and wife's 7mm-08 improved accuracy with just a 1/8 crimp.

 

[cdherman]

I tried crimping on a 340 Wby and my 6.5x55 Tikka. Did not achieve much improvement. Which is not to say I disagree with it at all. But its not a panacea either. My tikka already was shooting pretty good, but since it was throated with so much freebore, I wondered if a crimp would help. Didn't seem to.

The Wby has typical long Wby freebore. Refuses to shoot anything over 200 grains accurately. Like what's the point of a 340 if it cannot toss a heavy bullet. Well crimping did not seem to help there either. The Wby is too pretty for a muzzle brake or can, and just plain bludgeons you even doing load workup with a shoulder pad and a sled. Sometimes I think its inaccurate cause I am afraid of it.......

Anyhow, I have invested in a number of Lee crimp sets. Trying them out. Indeed, neither gun shot worse. Just not better.

 

[243winxb]

Sometimes you can have to much of a good thing.

When the powder is not burning correctly, a crimp may help.

 

[243winxb]

7.62 Crimp- Delayed Ignition/Free Space.

https://apps.dtic.mil/docs/citations/ADA341390 To avoid Delayed Ignition, use a mag primer, seat bullet deeper into the case, use a bulky powder that better fill the case. Increase bullet pull with a crimp, as a last resort. Crimps may hurt accuracy. Doing your own testing is the only way to know.

 

[ButterBean]

7.62 Crimp- Delayed Ignition/Free Space.

https://apps.dtic.mil/docs/citations/ADA341390 To avoid Delayed Ignition, use a mag primer, seat bullet deeper into the case, use a bulky powder that better fill the case. Increase bullet pull with a crimp, as a last resort. Crimps may hurt accuracy. Doing your own testing is the only way to know.

We have been calling it PIDT, powder ignition dwell time and once again if the LEE FCD used correctly I have never seen it hurt a load

 

[Hugnot]

I crimp bullets but use a minimum crimp. I avoid making a deep ring on bullets. My thinking is to avoid displacing bullet core, creating an imbalanced situation where bullet radii measured at crimp is variable. Bullet makers agonize on jacket uniformity & deep crimp rings might make for an imbalanced situation magnified by high RPM's.

The OP's groups sort of support this - "1/16 turn"

The Lee crimp die can squash bullets easily.

Edit:
Extensive & hard Lee Factory crimping might affect solid copper bullet roundness. OP - "But most certainly something is going on."

 

[243winxb]

Bullets with a crimp groove can be roll crimped or LFCD if so desired, but not a must do.

No crimp groove, taper crimp or no crimp at all.

The taper crimp is more forgiving when brass trim length is not all the same.

Personal choice. The target will tell what works best.