I've never had any of the crimp-on gaschecks, just the press-on type. Most of my stock is nearly 20 years old now. As long as I have done my part in the casting department, there have been no problems getting the gaschecks to stay on. Ah, yes, they have been all Lyman and used in 257Roberts, 6.5x55, 30-30, 308, 30-06, 32WinSPL, 8mm Mauser, 356Win, 357Mag, 38Spl, 40-82Win, 41Mag, 44Mag, and 45Colt. I really like cast bullets.
Regards,
Sweetwater