Lee factory crimp dies

midwestpredator

midwestpredator

Active member
I ordered a few of the Lee factory crimp dies for a project I'm working on and I have never crimped anything before so this will be new to me.

I'm interested in your experience with these dies and bottleneck cartridges. Did you notice improved accuracy, less accurate or no difference from crimped to non crimped ammo?
 
I've used one in 223 for an ar. Noticed not enough difference to bother with. Handgun ammo is a whole different story. Now I won't load a pistol cartridge without onen
 
Ditto dennyr for the pistols. I cast or buy my own pistol bullets occasionally one is over sized and will not chamber. The factory crimp die irons out the entire cartridge so it will chamber in any rifle or pistol (.357mag). I've never crimped any rifle cartridge (.223, .30-06, etc due to the fact that sometimes the shoulder gets swelled and they won't chamber. A chamber die might serve you better. I run all my rifle loads thru a LEE chamber die and find that some are oversized and the last thing I want is a cartridge jammed into the chamber of an AR and needing to mortar it to clear it.
 
I use them on some of my loads. Consistent neck tension certainly won't hurt accuracy.

I use a magnifying glass when initially setting up the die... as soon as I see physical marks, I stop. That way I have positive tension w/o damaging the bullet jacket.
 
I use them on all rifle loads going into semi-auto actions.
Don't see any relation to crimp vs accuracy or fps.
 
I have pondered this same question. I have been using the Lee FC dies for about 7 years. I used to always crimp my semi-auto rounds. That counts especially if they are my hunting loads.

As of late, I stopped crimping a lot of ammo. I burn through it so fast that I just eliminated the step. I cannot say that I have noticed any difference in point of impact, accuracy, or speed.

I would need to do some specific testing to see any major differences (if any).

TC
 
I researched this fairly extensively for 300blk and while lots of people us Lee FCD for auto loaders there are a few very informative and technical points out there made by some very interesting people on FCD vs taper crimp. I use FCD on my pistol rounds but i decided to try redding taper crimp for my future 300blk oh crap pistol... I also load for 6.8spc and 223 auto loaders and do not crimp those.

I have some issues with crimping .45 on my dillon with mr bullet powder funnel which flares the case deeper, similar to the lyman M die chambering in my Kart barrel vs the factory series 70 barrel. I tried the FCD and while my stuff now chambers the accuracy has fallen off a bit. So now I am contemplating deeper investigations into crimping .45
 
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Originally Posted By: Bowhntr6ptI use them on some of my loads. Consistent neck tension certainly won't hurt accuracy.

I use a magnifying glass when initially setting up the die... as soon as I see physical marks, I stop. That way I have positive tension w/o damaging the bullet jacket.

This is my thoughts on the topic as well. Just a slight crimp, for any of my loads that go into a semi-auto. Last year on a Pdog shoot, I pulled a round out of my AR-15, in 204 Ruger, which I had not been crimping, and found the bullet set back in the case. I didn't blow a primer, but I didn't need to see that again, so this year all 204 Ruger loads, have a slight crimp from a Lee FCD. I had a similar experience a few years prior, with an AR-15, in 223 Rem., but for some reason the lesson was lost on the 204 Ruger AR-15 project. Lesson re-learned.

As for the accuracy question, I have done a decent comparison, in several rifles, with crimped vs. uncrimped loads, and have not had a measurable difference either way. A couple of tests showed slightly better groups for crimped loads, and a couple of test showed slightly better groups for uncrimped loads. The difference was never more that a fraction of an MOA, so I chalked it up to human aspect to the test.
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So now my basic rule of thumb is crimp for semi-autos, and not for bolt guns, unless a load or a bolt gun give me reason to crimp them, as well. But always use Lee FCDs.

Squeeze
 
I think the factory crimp would be more of a benefit for cast bullet loads, where you had to take the bell out of the mouth of the case. That's what I used it for.
 
For rifle cases a consistent case length is needed if the length is all over then the crimp will be crappy as well.
 
Originally Posted By: BearFor rifle cases a consistent case length is needed if the length is all over then the crimp will be crappy as well.

The LFC die design eliminates crimping problems associated with varying case lengths.
 


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