crimping

User avatar
mtngun
Site Admin
Posts: 1637
Joined: Fri Feb 01, 2008 5:45 pm
Location: Where the Salmon joins the Snake

crimping

Postby mtngun » Sun Feb 17, 2008 5:17 pm

from the old forum:

I have read around and noticed that if we crimp too much on a cast bullet it destroys diameter as cast. Is this correct? If so is it possible to crimp heavy pressure loads i.e. 454, 475, 500 and still have a proper cast bullet as we cast it?

Reply: Yes and no.

The Lee factory crimp die for pistols tends to squash the portion of the bullet that is inside the case. The Lee die has a resizing ring at the entrance to the die. The resizing ring was intended to iron out any buckles in the case. The problem is that as the ring resizes the case, it also sizes the bullet that is inside the case. In theory, that's bad news for cast bullets, though some Lee loads shoot OK despite the bullet damage -- probably thanks to obturation.

This is not to be confused with the Lee factory crimp die for rifle cartridges that uses a collet rather than a resizing ring. The collet system is a great idea. IMHO, Lee should use the collet system for pistols, too, rather than the stupid resizing ring.

BAbore has reported that the Hornady pistol dies also squash the bullet. I have no experience with the Hornady dies, so I'll have to take BAbore's word for it. I would be suspicious of any die that has a resizing ring or that applies a taper crimp, in addition to the roll crimp.

Here is what I do for wheelgun loads where a good crimp is needed.

1) use a deep seated bullet design. The deep seated design gives the case more bullet to hold onto. Sometimes there are legitimate reasons not to use a deep seated design, like my 357 rifle bullet where I am trying to maximize powder space, but usually a deep seated design gets the nod in short barreled wheelguns.

2) turn the pilot on the case flaring die down to 0.005" - 0.010" smaller than the bullet. These pilots are almost always too big as they come from the factory. Basically, you only want the pilot to be big enough to iron dents out of the case, and to guide the flare straight into the case. You don't want the pilot to actually increase the case ID.

3) then put a modest roll crimp with a plain jane crimp die. I happen to use Redding dies (not their profile crimp, though).

4) use an inertia puller to test the bullet pull and to see if the bullet was damaged by the case tension. In some, but not all cases, a soft cast bullet will be squashed if the neck tension is excessive. So far this has only happened to me in the 30-06, but not in handgun cartridges. The only way to know for sure is to pull a bullet. Inertia pullers are cheap.

My standard roll crimp held the bullet much tighter than the Lee FCD, as measured by counting the number of whacks required to dislodge the bullet with an inertia puller on a 44 magnum cartridge.

User avatar
mtngun
Site Admin
Posts: 1637
Joined: Fri Feb 01, 2008 5:45 pm
Location: Where the Salmon joins the Snake

Re: crimping

Postby mtngun » Sun Feb 17, 2008 5:19 pm

Dan's correct on my view of the Hornady crimping die resizing the bullet. Hornady's die sets for the 454, 480/475, and I believe the 500 S&W come with a 4th die that resizes the case and roll crimps. It was sizing my cast bullets down as much as 0.003" in diameter. The most reduction was at the case mouth and tapered to the last driving band. This was on a .475 cal. 410 gr bullet. Accuracy was still good, but this was probably due to the GC on the bullet. Non GC bullets always had poor accuracy.

I did contact Hornady through a contact of Dan's and explained the problem. They issued a review of the die design but I couldn't get any feedback through the contact.

I just started using a Lyman M expander die on my 450 Marlin cases. When combined with a Lee FC die, I couldn't move the bullet with an inertia hammer no matter how hard I hit it. -- BABore

Another reply, perhaps by BABore? -- I found that the hornady crimp die was sixing my .4775 boolits down to .475. I honed it with progressively finer grits of wet sandpaper till I could no longer measure a difference in the pulled boolit. (Took a looong time!). The result was improved accuracy and no leading with plain base boolits. Also noted was improved case tension. I guess they designed it with condom boolits in mind.

jbquack1
Posts: 42
Joined: Sun Nov 09, 2008 8:25 pm
Location: Reno, nevada

Re: crimping

Postby jbquack1 » Mon Dec 21, 2009 8:51 am

I ran into the same issue with lfcd and hornady in my .45 colt.Of course my problem started with cylinder issues on my ruger bisley, i opened my chamber throats up using a chamber reamer to get consistent diameter as well as chamber depth.The next issue is what you are describing here.My fix included the use of a chamber polishing hone that i used after i got my cylinder finished.I honed the sizer ring on my lfcd(takes awhile as it is carbide)to clear my loaded cases, i also had to hone the crimp sleeve as it was doing the same thing, i use .454 diamter bullets and it would size the front driving band as well as the rest of the bullet out of spec for my chambers.I removed the crimp ring out of the hornady seater and just use it as the seating die and use my modified factory crimp die to roll crimp only.Many may wonder why i went through the hassle instead of getting new dies.1. I already had the dies and2. have a problem tinkering with things till they work.I went from some leading and poor accuracy to one ragged hole groups at thirty yards off a rest.The gun shoots better than i do so no complaints.jim

User avatar
mtngun
Site Admin
Posts: 1637
Joined: Fri Feb 01, 2008 5:45 pm
Location: Where the Salmon joins the Snake

Re: crimping

Postby mtngun » Mon Dec 21, 2009 1:33 pm

jbquack1 wrote:I went from some leading and poor accuracy to one ragged hole groups at thirty yards off a rest.

It's sure nice when the theory actually works in practice. :D :D :D

jbquack1
Posts: 42
Joined: Sun Nov 09, 2008 8:25 pm
Location: Reno, nevada

Re: crimping

Postby jbquack1 » Mon Dec 21, 2009 10:27 pm

Definitely, i learned that sometimes the gun isn't the only thing thaat needs to be tuned.

jbquack1
Posts: 42
Joined: Sun Nov 09, 2008 8:25 pm
Location: Reno, nevada

Re: crimping

Postby jbquack1 » Thu Jan 21, 2010 2:15 pm

Have been away for awhile, but this " crimp die throwing a wrench in the works problem" happened with my 0.475 linebaugh as well.I had alot of store bought bullets that worked well, but decided to have Dan make me a mold.I had also purchased a combination profile/roll crimp die from redding and the front driving band would come out with a shiny new finish at every pull of the handle.I had to do the same honing excersize with it to get good results.Again my .475 shoots better than i can, i got a ransom rest in a trade but don't have the inserts for these frames yet so my accuracy testing is basically useful for me.But i have seen a definite improvement in all pistols when i tweaked the dies.I talked to Lee precision today and was told that collet style factory crimp dies could be made for .45 colt as well as .357 mag (these are the calibers i asked about) at about 150 dollars a copy from existing bottle neck dies.I think the collet concept is the way to go, but i won't spend 150 bucks on them.I think a good guy with a lathe could take the 30 carbine die and modify it.This case is about the same length and these dies are about 10 or 12 dollars from midway.

I notice my post have not been complete as to curing my problems.The leading in any case caused by this also went away.jim.

User avatar
mtngun
Site Admin
Posts: 1637
Joined: Fri Feb 01, 2008 5:45 pm
Location: Where the Salmon joins the Snake

Re: crimping

Postby mtngun » Thu Jan 21, 2010 4:08 pm

Thanks for the update on crimping dies.

I don't remember having this problem with crimp dies "back in the old days". Seems like the die companies have snugged up their tolerances. That's all well and good for jacketed bullets, but causes mischief for our oversize cast bullets.

jbquack1
Posts: 42
Joined: Sun Nov 09, 2008 8:25 pm
Location: Reno, nevada

Re: crimping

Postby jbquack1 » Fri Jan 22, 2010 2:10 pm

Your right about that, of course i personally have become more sensitized to bullet "fit issues" since designing bullets and wanting to wring more accuracy out of my revolvers.My old thought process was that the bullet manufacturer and the gun makers had everything "standard" so you just go get a box of shells and thats the end.jim


Return to “equipment”

Who is online

Users browsing this forum: No registered users and 1 guest

cron