An idea I tried years ago was to cut .600" discs out of brass shim stock and center them on the bullet sizing die under the lead bullet. Running the bullet through the sizing die produced a close approximation of a gas check which remained attached to the recovered bullets. Cutting a .600" recess in the face of the die made it much easier to center the discs, but is not essential. This technique obviated the need to create a special bullet with an undersize base to accomodate conventional gas checks.

In these days of super adhesives, gluing a .585" brass disc to the bottom of the bullet would probably do just as well, but would not prevent leading.