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View Full Version : PC and .357sig- dimensional change benefits and drawbacks



totalloser
02-23-2014, 03:16 PM
As most folks who load .357 sig know, ogive and bearing surface vs neck length is a bit of an issue for OAL. My first attempt was with military 115gr pulled bullets and I was unable to make a reliable cartridge. OAL set to fit the mag was so short that the ogive robbed enough bearing surface in the neck that rough handling (even chambering) would tend to cause a setback leaving the bullet loose in the case.

So how does this pertain to PC? Well, when you add PC, the ogive gets coated appx. .001" and the taper at the beginning of the ogive is very gradual, so the PC affects the length of the neck bearing surface which you don't lose in sizing.

To test real world effect of this, I took a once fired shell and Lee 125 grain round nose (lee90457) measured the following:
Length of lead: .573"
Length of PC : .578" (gravity buildup on nose)
OAL with *nose in* (to hit ogive)
Lead: 1.153"
PC: 1.160"
Shell: .862"

A little basic math indicates that the bearing surface increases by about .007" in this boolit, which brings it pretty close to ideal with this shell putting OAL at 1.143" with PC (Book OAL is 1.140") for a minimal gain due to buildup on nose from gravity application which can vary greatly.

I have loaded with this boolit with yellow HF PC and shot as a test for the boolit vs polygon barrel, but didn't like being at the edge of OAL vs neck contact so only did a test so far. For various reasons I have been reluctant to purchase a truncated cone mold, but have decided to mod this mold for HP and will post up results.

The plan is to machine a pilot jig to guide the drill bit and use the new style lee decap pins for HP pins precision press fit into steel sleeves. I will post a pic when I get to it- either a sooper dooper modification or a destroyed mold, but thought I'd share #s on my findings. The HP should knock the OAL length back enough for .357sig for two reasons: .005" of PC on the nose will probably drop to .001" (PC upside down) and the HP pin should knock it back about .005". .010" would be an acceptable cushion for my taste.