Gas Check Thickness

[sparky45]

I need to buy some gas checks for a Lyman cast boolit (311291) and I need info concerning the size of check to buy. In 30 cal there are listed thicknesses of .008 - .014. The shank of this boolit measures .283-.284. Do I buy the checks made of aluminum in .014 thickness or smaller?

[tjones]

Factroy seem to be about .015. Gator, or sagesoutdoors.com seem to have most anything for you to sample.
tj

[sparky45]

Well, I guess my question now is : given that the shank is .284 in size, why the different thicknesses of checks. Are you supposed to use a check that will be the same size as the completed sized and lubed boolit?

[Sonnypie]

I use that exact mold model (http://www.lymanproducts.com/lyman/bullet-casting/mould-details-rifles.php?entryID=47) for my 30-06.
Mine is a single cavity mold.
I've been successful making gas checks with .011 -.020 with various materials.
My bullets from my 311291 mold drop at .314", with a .286/.287 gas check shank.
These are cast with Lyman #2 alloy from Rotometals, so I'm pretty sure of the alloy. (No huckleberry fin mixture.)
Once gas checked and sized, my bullets all run .3105 (because that is .002 over my bore size, and what I honed my sizer die to).

Material .011 to .014 has worked very well as far as setting on the as cast shanks.
And Hornady gas checks (copper) use .017 thick material for their commercial gas checks. Those were what I used before I began making my own.
I have not had good results with anything under .011" holding to my bullets. Not .010 AL, nor .008 AL, nor .007 copper, nor .006 copper. They fall off.

I have had good results also with .016"AL, .017 copper, and even with .020 soft AL.

So .011" brass, thru .014" Aluminum, has worked best for me and is what I would recommend to you since you seem to have choices.
You are welcome to look at some of this HERE (http://s1195.photobucket.com/albums/aa382/Sonnypie/Gas%20Checks/Gas%20check%20making%20project/), HERE (http://s1195.photobucket.com/albums/aa382/Sonnypie/Gas%20Checks/Ians%20coil%20materials%20015AL%20and%20017CU/), and HERE (http://s1195.photobucket.com/albums/aa382/Sonnypie/Gas%20Checks/).

[sparky45]

Thanks for the reply Sonny. I have been puzzled over the sizing issue vs/vs "If I size a .016 GC onto the .284 shank of my boolit(311291) will the GC crush the shank or squeeze it into a different dimension, say elongate the boolit a bit?" I guess what I am concerned with is that I will be shooting these through a Micro Grove Marlin 30/30 barrel which slugged to be .309 and I am sizing this boolit to .311. Will a GC of .016 thickness create a base thickness of .316 or will it conform to the sizer die dimension of .311?
Again, thanks for your help.
Sparky45

[Sonnypie]

In my experience the O.D. of the bullet and gas check (The assembly) is the die size.
I size everything I cast to be assured it is as good as I can make it.
I haven't checked to see if the bullet "grows". I'm fairly confident it does not.
Not any appreciable amount.
The method of a Lee sizer die places the force at the base of the bullet being sized and pushes the gas check hard to the base as the cup is sized (squished) to the shank.
You may be over thinking the whole thing. :veryconfu

[Dan Cash]

I need to buy some gas checks for a Lyman cast boolit (311291) and I need info concerning the size of check to buy. In 30 cal there are listed thicknesses of .008 - .014. The shank of this boolit measures .283-.284. Do I buy the checks made of aluminum in .014 thickness or smaller?

Go to http://www.thegascheckstore.com/ and read what he tells you under the heading "Gaschecks." There it explains how to measure for your gascheck if very clear terms. He will also sell you the size check you want.

I have no connection to or interest in this firm.
Dan

[sparky45]

I'll be sizing on a Lyman 4500 with a .311 sizing Die, hope it all works out with the 0.014 Gas Checks I purchased.
Thanks all,
Sparky