How far can you size down a gas check?

[am44mag]

Here's a question for you guys. Let's say I have a rifle with a 0.330" bore, and a mold that drops at 0.340". If I was to use 338 caliber gas checks and then size the boolit down, should I expect to have any issues?

I have an old M95/30 Steyr Mannlicher that I'm wanting to start reloading and casting for (running low on my stock of milsurp ammo for it), and it's odd bore dimensions are causing me to have to get creative.

[earlmck]

I happily use .264 checks on .257 boolits, which is about the same percentage size reduction you are talking. I think you'll be just fine.

[MT Chambers]

Doesn't matter what the bullet's dia. is...it is the diameter at heel, where the gas check goes. If you can fit it on the base, it will size down the same as the bullet.

[Rcmaveric]

Material thickness of the check matters as well as if the check fits the bullet shank. Subtracting your gas check shank diameter from the bullet diameter will tell the minimum gas check material thickness. My .270 checks and .264 checks will interchange bullets and fit. The material thickness is different though. The .270 ones are thicker. So i can use the .270 checks on my .264 bullets (and i have, no problems) but i can not use the .264 checks on the .270 bullets.

[n.h.schmidt]

That's a lot of size down. It can work though. If you size with a reloading press and a push through bullet sizer. It would need a generous taper at the opening to allow it to go through. If you water drop to get harder bullets,do that after sizing. You can heat them in a oven to harden. I have reduced .325 8mm bullets down to .312 for paper patching. That's a lot to do in one pass.
n.h.schmidt

[JonB_in_Glencoe]

I would try sizing some down (in 2 or 3 steps) without GCs installed and see what the base looks like, you might get lucky and end up with a adequate PB boolit.

[am44mag]

The mold I'm looking at (NOE 340-205-FN-Q5) can be had in a PB configuration. I was wanting to be able to push the boolits to around 2000 FPS, but after some thinking, a PB powder coated boolit might be the better option. I will be experimenting with sizing down .323 boolits and GCs to 0.317 for my Arisaka though.

Thanks for the helpful info fellas.

[Dragonheart]

For 2000 fps I wouldn't go to the time and expense of a gas check mold; if you PC it is not needed. The only benefit is a gas check, if properly installed, can provide a flat base, but you should be able to acheive that as the PC can fill small imperfections in the base.

[beagle]

Annealing the GCs prior to trying a big downsizing my aid you as well./beagle