" I found in my rifles that cast fired at velocities over the 1600 fps range required gas checks to maintain accuracy. "
Texas Mac, That seems to be about the "upper limit" for not using gas checks due to leading. Gas checks are indeed a wonderful thing when used correctly. I personally don't use them on my .44, but then again when shooting cast I'm usually well under 1,000fps, sometimes only 900 or so. I do use them on my hunting rifles (the three that I cast for, and hunt with) I have recovered 3 bullets from game with the gas check intact and the lead nose dubbled in caliber.
I have pushed cast bullets w/gas checks to almost 2,100fps. with no signs of leading. I have also pushed loads to 1700 w/o gas checks that took months to get the lead out of the barrel.
Gas checks are a necessary evil in my mind, but after a while you get to like them, and start respecting them for what they do.
Russ