CRIMPING QUESTION ON CAST BULLETS?

01 August 2002, 03:38

dan belisle

Well, it could. It would depend on other factors as well. What the load is, oal, case length, etc. It would certainly raise pressures over the same load in an uncrimped case. For 45 ACP I only use a taper crimp, I find this works well in all my 45 autos. FWIW - Dan

01 August 2002, 04:16

Pecos41

Trophy - The .45 ACP is one of those cartridges the books warn should NOT be crimped as it headspaces against the case mouth. As Dan suggests, use a "taper crimp" if you must.

As far as dangerous pressures, I've never seen any significant pressure variations with cast bullets because of crimping.

So, to answer your question, I'd say you better worry about headspace, not pressure. IMHO [Smile]

[ 07-31-2002, 19:17: Message edited by: Pecos45 ]

01 August 2002, 04:56

Recono

quote:
Originally posted by Pecos45:
Trophy - The .45 ACP is one of those cartridges the books warn should NOT be crimped as it headspaces against the case mouth.

I've heard that, too. I doubt it. I doubt that most .45 ACP cartridges headspace on the mouth, since I've never seen any that were anywhere near .898" long. Do they headspace on the extractor?

Some buddy who know?

Of course, if you use them in an S&W Model 25 (NOT 625) or M1917 without clips, THEN for sure they headspace on the mouth, but I'm not so sure about autos.

01 August 2002, 05:21

Bill M

I believe that they do headspace on the mouth of the case. Remove the barrel from a 1911, and drop a loaded round in the chamber. The "face" of the cartridge should be even with (or very slightly below) the "squared" tang portion of the barrel for proper headspace.

The danger in over/crimping the mouth of the case is that the crimped portion of the brass may slip inside the "end" of the chamber (where it should stop for proper headspacing), and thus the brass may not be able to expand enough to let the bullet go, creating high chamber pressures. Similar to using brass that is too long for a particular chamber.

Regards, Bill

01 August 2002, 05:22

Pecos41

Recono - I'm just parroting what the good text books tell us about the .45 ACP. A rimless case headspaces from the case head to the shoulder, which is why you don't want to set the shoulder back. But the 45 ACP and all other straight wall rimless cases like it have NO shoulder. So, they headspace from the "head" to the case mouth. Thus, putting a hard roll crimp on that mouth is the same as setting a shoulder back.

This is how it was always explained to me.

Now to tell the truth, I've been guilty of using some pretty nasty roll crimps and everything else on my .45 ACP loads to keep the bullets from moving and I've never had a problem with headspace. I don't think a normal roll crimp on this cartridge is going to move anything enough to be significant. So, frankly I think the whole issue is pretty much horse feathers...unless someone just totally alters the shape of the case in some idiot way. But I don't want to come on here and formally tell anyone not to worry when the big guys who are supposed to really KNOW all this stuff say the opposite.

But I don't really think Trophy has anything to worry about...certainly not from pressure.

01 August 2002, 06:07

<BigBores>

I use a taper crimp and have never had a problem. I suggest anyone crimping ACP loads do the same. I happen to use a Dillon die set which comes standard with a taper crimp on all auto cartridges, and a roll crimp with all revolver cartridges. I believe you can still order only the crimp die from Dillon and keep your whatever brand die set you are currently using.

01 August 2002, 08:27

KLN

Crimp will not directly increase pressure, but, a heavy roll crimp can actually loosen the grip of the case on the bullet. This can potentially allow the bullet to be forced farther into the case during feeding, which can dramatically raise pressure. A taper crimp avoids this problem, provided your case is tight enough to begin with.