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robocop10mm 12-16-2012 05:51 AM

.40 S&W to .357 Sig
I had heard you cannot simply neck the .40 S&W to .357 Sig because it will be too short. I have thousands of .40 cases and was pretty much out of the .357 so I decided to experiment.

Lubing the .40 case with a bit of Imperial Sizing Wax, I ran a few .40 cases through the full length .357 die. The .40 cases started at .850 and ended up .860. Yup they grew 10 thousandths. The .357 Sig standard case length is .865. I'm still .005 short, right?

Even though the .357 is a bottleneck case, it was designed to headspace on the mouth. It CAN be loaded to headspace on the shoulder, if desired. I adjusted the die to set the shoulder to allow the case to headspace on the shoulder in my barrel.

I lose .005 in the neck so bullet hold will not be quite as good, but I plan on using these for a moderate load using a 125 gr RNFP hard cast bullet. I will crimp a bit more than normal to keep the bullet secure. Since I am not relying on the mouth for headspacing that will not be an issue.

I will load some up (as soon as I replenish my Wheel Weight stock) and let you know the results.

msup752 12-16-2012 01:34 PM

I used to have several .357 sig pistols. The brass was scarce but I had an unlimited supply of .40 brass from the State Police.
I resized it and fired near max loadings using Power Pistol and Ranier 125 gr plated bullets with zero brass issues. Some oddly shaped bullets would not crimp into place well (golden saber).
I had a Sig P228, an H&K USP, and a Glock. All are gone now but I passes on my brass to a Walther PPS owner and it is still going strong.

robocop10mm 12-16-2012 02:37 PM

As I am shooting them through a G-20 with Lone Wolf conversion barrel, I am not restricted in my bullet selection. The 10mm mags allow longer loadings

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