357 mag cases resized

[passgas55]

Today if I get time I am going to make 6 test dummy cases. A fired 357 case(smokeless) is .379 dia. A sized case is .372 dia. I want to size my cases for consistency for use with the 3 guns I will be using. I also want to minimize how much of the case dia I size to.

At first I was thinking getting another sizer and having the sizing ring machine to a bigger dia. Then I remember the Lee factory crimp tool has a sizing ring built into it. It sizes the case to .378.

If all goes well with the test dummy rounds in the single action and the Rossi M92 rifle I will load 50 rounds to try in one single action pistol. If all 50 rounds can be shot in one pistol in one session without any issues I will load another 50 to try in the rifle.

I hope this works. It should help in sealing the chamber which is what I am aiming for over a fully sized .372 dia.

[rfd]

i don't understand your motives. if you are building black powder cartridges for a multi round firearm, there will be a need for crimping so each round is built on a the cartridge standards, which means all rounds should fit firearms with that cartridge standard. this means sizing, expanding, full up charging with some compression (bp) and then the seat and some amount of crimp. i dunno about bpcr for handgun cartridges, but with new brass for bp rifle cartridges i do fire form simulation neck expansion with a straight wall expander.

[passgas55]

I just did some lee sizing of once fired brass. Some of the cases were to tight at the base. I am going to resize the cases one time with my regular dies then after only shooting bp in these cases size with the lee crimp tool. I understand about the yes they will be crimped, compressed, expanding, etc. I am looking to get away with the least amount of resizing the diameter of the case.

[rfd]

resize to cartridge case spex once. straight wall expand to both simulate fire forming and to accept a thumb seated grease grooved bullet (this may be a .379 or .380 or .381 expansion plug). prime, charge, wad, compress, push in sized/lubed bullet. crimp with a taper die. fire. from now there PROBABLY will be NO case working required other than cleaning, prime, charge, wad, compress, push in bullet, taper crimp. this fire forms to the chamber, be it cylinder or action, so their MAY be firearm variations. i dunno any other way around this (fire forming) other than yer gonna hafta resize back to case spex after every firing.

[leadman]

My concerns would be the bullet "jumping" the crimp if bullet pull is to light in the revolvers and bullet being pushed down in the case in the lever action. A case full of bp would prevent the bullet being pushed down in the case if the case is full to the base of the bullet.
It may take a bit of work to get these to perform well in both guns but I can see your point in doing this.

[justashooter]

the OP seemed to be concerned with gas seal. in my experience 357 mag brass does not always expend well and seal gas at the case mouth. the brass is stiffer than traditional thin walled brass like 32-20.

[greenjoytj]

My first 357 Mag die was a Lyman carbide set. The Lyman carbide sizing die really shrunk the diameter of the whole case above the solid case head. With the seated bullet stretching the top of the case the cartridge had a weird wasp waisted look. I solved this over working the brass problem with a Redding dual ring carbide sizing die. Now my 357 mag cases look smoothly parallel with just a slight swelling were the bullet sits. I still use the Lyman M die for case mouth expansion prior to seating lead bullets.