Seating & Crimping Cast Boolits in .357 Sig

[justindad]

There's a unique challenge with seating lubed cast boolits into this bottleneck case: the neck tension is so low that it cannot overcome the pressure that is developed inside the case when you seat the boolit. It's literally a piston. I confirmed this when I held a case and seated boolit in the jaws of my calipers. I could pinch the jaws together with very little force and seated the boolit deeper, and then the boolit would rise up out of the case as soon as I released the calipers. Up & down, up & down - just like a piston. The grease helps to keep the air sealed and reduces friction in the neck. I've seen this with the Lyman 9mm Devastator and the RCBS 9mm-147-FN (with two grease grooves, which makes it worse). Grease grooves inside the tiny neck just further reduce neck tension.
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I was using AA#7 with the Devastator and I would just work the boolit until the air could escape. Now I'm doing a compressed charge of Enforcer with the RCBS, so I can't just work the air out. So, I decided to do a half crimp & seat simultaneously. Know that I generally hate seating & crimping in one step. I have some cartridges that I seat in two steps, and crimp in a third step (which is outside of the scope of this post). The first crimp is just barely enough to keep the boolit from acting like a piston; in fact, I can still easily push the boolit deeper into the case by hand.
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Then, I wait a day to see if the overall cartridge length grows. Confirming the length hasn't changed, I then do the second crimp using the Lee collet style FCD.
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I want to point out that you have to be very careful to not over-crimp the .357 Sig cartridge. Over-crimping will cause the tiny neck to flare out, and you lose neck tension. I once over-crimped a plated bullet that would spin in the case. I could not push in or pull out the bullet by hand, but it would easily spin in place. This cartridge has to be crimped just right.
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Also, seating & crimping simultaneously violates the guidelines in Lyman's 49th reloading manual. This process I described should not be done without previous experience and caution.

[hermans]

justindad, very very interesting. A friend of mine is trying to get his 303 British rifle to shoot cast boolits and we have never thought about this before. Thanks for sharing!

[Bill M]

I have not experienced that problem, maybe my expander opens the case more than yours!
When I started loading 357 sig, the only carbide dies were from Dillon, so I used them but found it easy to push the bullet into the case. I bought a Lee crimp die, but still had problems until my friend Pete machined the die for a tighter crimp. I have since shot many thousands of cast, and jacketed with no problems.

[45_Colt]

Not sure if I can help. But do load 357 SIG for a 1911. First off I would find a boolit that had a crimp groove. That could be used with the Lee collet crimp die. Both to keep the boolit in the case, and to prevent setback. This will likely require a new boolit design.

Setback has been my biggest issue, and broke down all of the previous cast boolit loads due to it. Have been working on jacketed (I know, I know: but one thing at a time) loads with an added cannelure. This made a world of difference.

OTOH, if the cast boolits are being pushed out, maybe the neck tension isn't enough? There isn't a lot of neck, check the neck expanding die diameter. A smaller one may be the ticket.

If you can keep push out to a minimum, and have a cannelure to crimp into, your problems may be solved. Of course the crimp needs to follow the seat right-up-quick.

45_Colt

P.S. on the funny side, I though that a small hole drilled the length of the boolit would prevent push out. But that is a rather ridiculous solution, but funny. Thought I'd kick it out there for anyone that needs a chuckle...

[justindad]

Thanks 45_Colt. I once used a 124 grain lead bullet from Hunters Supply that had a cannelure, with good results. I designed a PC mold with a very slight cannelure, but Accurate Molds would not reply to my emails about it. The process I have now is working, but I cannot get max velocity loads, because the max load of Enforcer is very compressed.

[20:1]

I've had situations where heavily compressed powder pushes the bullet back out a bit with 9mm cases. Taper crimp is almost worthless against this because it's intended to prevent bullets from pushing into the case during the feeding cycle. I haven't tried to cram a huge dose of Enforcer into a 357 case yet, I'm still focusing on the original Accurate data for #7 & #9. I suspect your powder volume may be causing this, not trapped air.

[justindad]

The powder is not compressed - it’s air pressure. I measured the depth of the powder to confirm. Besides, if AA#7 was compressed, that gun would probably be destroyed.

[fredj338]

I havent had issues with TC lead bullets in my 357sig. I use Dillon dies & taper crimp. I have heard the LFCD does a good job but havent tried it yet.

[TRAPDOOR 4570]

I assume that you know this but Lee makes a collet factory crimp die for the 357 SIG. When I was using the Winchester ‘92 in 38/40 I never had any set back even with a full magazine. I even tried firing the full magazine except for the last round reloaded and did it again. The last round hadn’t budged in length. Also with jacked rounds they crimped almost as easily as lead slugs. Also it sounds like your die is not sizing down enough or the expander is to big. Just my 2 cents.