I have been using Hornady Copper Gas Checks on all of my cast lead boolets for years pretty successfully. They fit the RCBS, Lyman and LBT molded boolets very well and when crimped on, they don't come off even after hitting deer and other stuff. They appear to have a thickened lip that crimps into the boolet base. I have recently looked at purchasing some of the aluminum gas checks that are far cheaper than the Hornady's, but have read stories here on this site that they don't crimp on well and stay on like the Hornady's. And I looked at the gas check makers that allow a person to make their own, and they don't have any sort of method to produce this thickened lip around the crimping edge. So I have been reluctant to buy one of them if they don't really make a well-formed gas check that crimps on properly. So, my real question is I guess, are there any produced aluminum gas checks sold commercially that are cheaper than the copper Hornady's and are produced with the thickened crimping edge so they don't come off? And are there any production equipment sold that produces a properly formed gas check out of aluminum?