I know that I can buy gas checked 10mm bullets from Double tap. I also know that I can buy gas check making equipment from Corbin so that I can produce my own 10mm gas checks. I am wondering if there is any source for ready made 10mm/.401 gas checks. I cast my own bullets for the 10mm and my lead-bullet velocities are limited by the lack of gas checks. Even if I had to have a custom bullet mold built (one that casts bullets well-suited for gas checks) it would be worth it. Does anybody know of any sources?