LEE 358-125-RF in 357 SIG

[McFred]

I spent the weekend working up a load for a Glock 31 in 357SIG using the LEE 358-125-RF. The alloy is air-cooled wheel weights, sized to .358" and tumble lubed with 45/45/10.



I used weight-sorted Federal .40 S&W range brass with Remington 5.5 primers. I was surprised to find that these small cases vary by nearly 500mg (~8gr). I cherry-picked a set of 150 that weighed within 50mg at an average weight of 4.140 grams. I care about this as I am using a *full* case of WC297 surplus ball powder to set the bullet on. Variation in case capacity affects the seating depth. Bullet setback from the short neck is a non-issue.



In my G31, these bullets' ogive touch the end of the chamber at 1.130" overall cartridge length. At 1.130" with my selected Federal cases, I can fit 12.75gr of WC297, which burns cleaner the more you put in. In testing, I ran up to 14gr jamming the projectile into battery and got no signs of over pressure, yielding 1377fps average, unfortunately, this OAL will not function reliably in this semiautomatic.

With 12.75gr the pistol seems to function well from a magazine and after 50 rounds the polygonally-rifled bore is as shiny as new. Average velocity is 1135fps. With 12.75gr commercial Win 296 it leaded the bore and yielded 1113fps average as a point of comparison.

Primers look fine:


Some considerations:
• I'm actually using the projectile, neck tension and the powder column to control headspace, not really the case mouth or the shoulder.
• I'm bumping the shoulder on the cases back about .010" from fired cases. This may seem excessive, but it gives enough slop that any powder-fouling in the chamber affects function less than with tighter chamber tolerances.
• Different alloys or lubes may permit different loading procedures, this is what's worked for me. 12.75gr W296, 12.3gr AA#9, 6gr-7gr Unique, and 4.5gr Bullseye all leaded the bore at similar low pressures and velocities. In an aftermarket cut-rifled barrel I never was able to keep it from leading the bore.

Lastly, the fireball seems appropriate for Independence Day weekend:

[Atonic]

So you don't have any issues with the bullet being .03 oversize?

[sukivel]

How was accuracy?


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[McFred]

So you don't have any issues with the bullet being .03 oversize?

No. It's .003" oversized from nominal, but it's lead, it squeezes down. I haven't slugged the bore so I left them fat.

How was accuracy?

I do not consider myself a pistol shooter. I like long guns with big, clear, optics with a lot of magnification. I don't even know what a common standard for pistol accuracy is, but here's what I stepped outside and shot 10 minutes ago:



8.5"x11" sheet of paper, shot at 10 yards off a sandbag.
The big holes are the firebreathing Glock.
The small holes are a .22lr Ruger Mk2 target pistol: better sights, better trigger, and less clockwork off a sand bag. I'm almost embarrassed to post that. I have rifle groups that are half that size at 200 yards.

[McFred]

Here's the same target with another 5 shots from the stainless cut-rifled barrel:



It has a tighter chamber, is reluctant to go into battery (requires a shorter OAL) and leads the bore, but the first 4 shots were touching. The last one was 6 o'clock low.

[cwlongshot]

I bought this mold just for the 357 SIG. i have been using it for almost two yesrs. It works great with a number of powders at any sane velocity. Zero issues. I powdercoat mine.

CW

[sukivel]

I share the same sentiment on rifle shooting with lots of magnification. I think that pistol shooting is good. Heck at 10 yards if they are all on a sheet of paper that’s all you really need.

I use that same mould for 9mm and it works great. Six banger, pc’d, sized to .357 with 700x.


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[Nobade]

Hey McFred, you and I have some similar loading techniques. And have reached similar conclusions - a bunch of slow powder can make boolits work where less of faster powder will cause leading. Been using that same boolit in my 9mm over AA#5 with extremely good results. Keep it up!

[McFred]

Hey Nobade!

If I could get ≤2gr of something to work then that'd be fine, but I can't, so slow and full is the alternative.

After all the dinking around on this particular project, I'm begining to see why people like revolvers for cast stuff.

I'll keep in mind your comment about AA#5 and the 9x19. I might be supplying projectiles for a friend soon for their 9mm and they use #5.