My first experience making gas checks was with the early version of Freechex, the kind that you This summer I have sent in the neighborhood of a thousand .30 caliber cast boolits down range fitted with homemade gas checks. I have just started making gas checks for pistol.
would whack with a hammer or club. I no longer own such items.
My experience this year has been with PatMarlin’s Checkmaker in .30 and .35 calibers. I have been very pleased with the gas checks that I have made with the Checkmaker.
I have developed several theories about home make gas checks.
Theory #1
With bore riding boolits the gas check must act as a driving or guiding band. The fitted gas check should be the same diameter as the boolit band above it. The gas check should be swaged onto the boolit shank during the sizing operation.
The minimum thickness of the gas check can be calculated as follows:
T = minimum thickness or gas check material
SD = diameter of sized boolit
GD = diameter of gas check shank
T > (SD – GD)/2
( “>” means greater than )
Theory #2
With full bore boolits such as pistol or Loverin style boolits (non bore riding) the gas check needs only to be secured to the boolit . The bearing length of the boolit overwhelms the bearing effect of the gas check. I cannot prove that it makes any difference, but I like the gas check to arrive at the target still attached to the boolit. My experience with the .357 Magnum has been that the thickness of the gas check has minimal effect on the boolit accuracy. My testing to this point has been that 0.008” lith plate checks performed a little better than 0.014” aluminum.
OK guys have at it! I am sure that I will get plenty of comments and feedback about my theories.