How about a couple of thosands?

I think the traditional roll crimp most rifle dies have is the culprit for case bulges and loose bullets.
Lee's collet crimp squeezes the edge of the case into the bullet, crimp groove or not. I has enough power to push the case into the bullet even with out a groove. I have crimped Hornady GMX bullets.
I have the Lee die for several of the calibers I load for.
On some cartridges it seems to improve accuracy as well as velocity variations, lower SD's.
On others I haven't seen much difference.
I plan on much more testing in the future.
I can't really recommend roll crimping rifle cases of small diameter. Lee's collet die will provide a good crimp on these smaller diameter cases.
Om my 44 mag's I have always used a firm roll crimp, I recently got a Lee collet die for the 44's I haven't tried it out to see if it works better or worse.
With the little amount of using the Lee die, I have to agree with Lee that case length isn't as critical as with a roll crimp.
I have a Lyman 310 tong tool set up for the 44's that make very accurate ammo. I think a big part is the way it crimps. I seat the bullets and crimp together.
I have the seat/crimp die adjusted so on the shorter cases the handles won't touch. This lets me control crimp pressure very well. When longer cases get the bullets seated I can still get a consistent crimp. As on the shorter cases I can feel the case roll over into the crimp groove. On a regular press you have so much leverage you lose this fine feel.
There are people that sell a torque wrench specifically to apply consistent crimp pressure.
With one of those and a Lee die, you can get precise crimps, from nothing to as heavy as you want, then test each level for effect.
As in take an accurate load loaded as you usually do then have say ten round sets with varying crimps and see for your self.
You may find it doesn't help or maybe it does.
Can't hurt to try.
Leo

I agree, if one must crimp, a taper crimp die is the way to go.

quote:

Originally posted by Stonecreek:


Crimping is rarely indicated and should be avoided except with certain rounds and guns.

No reason given for this statement. Disregarded.

Lee Factory Crimp all the way!