Gas check diameter

[faraim]

I'm a fairly new caster. 40 and 44 caliber for handguns so far. I decided to purchase some cast rifle bullets for my .308 since gas checks are a mystery to me. On one the bullet diameter is .310-.311, but the gas check is .312-.313. I'm not concerned using a relatively soft .311 lead bullet in a .308 bore. However, the gas check diameter bothers me. Have any of you folks pushed a gas check through a barrel with a .005 difference?

[fcvan]

First question would be what is the shank size of the cast boolit. I make my own, and use different sizes of aluminum flashing for the proper size needed. I also anneal the aluminum before forming the cups. Annealing is a 15 second dunk into my casting pot for 10 strips, enough for 100 checks, I usually do enough for 1K.

Slightly larger checks as you have have mentioned, they generally crimp down to the size of your die. I load and size for .310 in my 30 cal cartridges, .312 for my 7.65 Mauser.

[mehavey]

the bullet diameter is .310-.311, but the gas check is .312-.313.

When you assemble/size the bullet gas-check combo, everything then sizes to the same diameter.
-- BUT --
Have you bought bullets with a gas-check shank, or plain-based ? (if plain based, a gas check won't fit anyway)
Have you bought bullets already gas-checked, and the assembly is not uniform?

[DHDeal]

Springback. Harder alloy bullets springback more than say 20/1 too. In a perfect world with dead soft checks, they'd be the same size as the bullets. It not being a perfect world, you're sizing 2 different alloys and they don't come out the same. If I were to measure any of mine I'd bet that my checks would be a thousandths over the bullet too.

Lots of threads about annealing gas checks. I intend to, but never seem to get around to it. Guess what, my GC bullets shoot great. Give yours a try or size them a tad more if you would feel safer.

[charlie b]

To use gas checks they need to be crimped (sized) onto the bullet. And, as stated above, the cast bullet needs to be a design that accepts a gas check (it has a smaller dia base for the gas check to fit).

You choose a size die based on the dia of your barrel. It needs to be the same as the groove dia or slightly (.001 or .002) more. The size die I use for my .308Win gives me a .310 dia bullet and the groove dia of my rifle is .309.

Hope that helps.

[popper]

GC shank should be ~0.297 or so. Snap them on and run through ~310 sizer. Goal is 310 body and GC OD.

[stubshaft]

Once you crimp and size it, it will not be .005" different.

[44Blam]

I make my own and some calibers are a little bigger than the shank for my boolit, but when I size them it folds it down and sizes it.
I've been using 28 ga dead soft copper - they work great.

[faraim]

Thanks for the replies everyone. I didn't know which mould design to purchase so I purchased gas checked bullets from commercial producers. On one group the bullets were .311 and gas checks were .313. I thought this was concerning. Now I'm wondering if the bullets were plain based with the gas checks forced onto them.

[mehavey]

If they sold you gas-checked bullets, they were of gas check design.
Not to worry. (I think)

[earlmck]

DHDeal told you right -- it is "spring back" after going through the size die. Most of my gas check boolits come out a little larger in the gas check area than in the body, just because the copper will spring back a bit more than the lead alloy. Shoot 'em -- they'll work just fine, and there is no pressure consequence from little size variations in cast/checked boolits.

[gwpercle]

Thanks for the replies everyone. I didn't know which mould design to purchase so I purchased gas checked bullets from commercial producers. On one group the bullets were .311 and gas checks were .313. I thought this was concerning. Now I'm wondering if the bullets were plain based with the gas checks forced onto them.

Look at them and see if there is a groove above the top edge of the gas check .
A boolit designed to be gas checked has a recess that goes all around the base and the recess is usually higher than the gas check ... so you can see the remaining groove above the edge of the check.
Place a check on the boolit base , run it through you boolit sizer and carry on .
Everything will work out fine !
Gary

[mehavey]

I purchased gas checked bullets from commercial producers.

If you don't mind, where'd these bullets come from (and what weight/style)?