Originally Posted by
StarMetal
John,
I make my own gas check making tools. So far I have them for 22, 6.5, 7mm, 30, and 45. I use aluminum flashing from the hardware store for 22's up to 6.5, and thicker aluminum for 7 up to 30, and flashing again for the 45's that take a thin check. With that said my target backstop, which is railroad ties stacked to form a big letter C, filled with dirt, and one inch oak front. I have recovered many bullets with my checks still on them in all those calibers. I think the reason may be as the cup is formed in the forming tool the bottom of course is very true and clean, but the lip will get wrinkles or serrations if you on it and I believe these crimp onto the bullet. Another member said those serrations help clean/wipe lead out of the bore better.
Joe