10 Gauge Lifter or Top Lever?

[Dean Romig]

There seems to be some confusion between chambers that were cut for metallic (often brass) cartridges (square chambers) and the 90 degree angle of the action flats intersection with the standing breech (also referred to as square cut) on the earliest lifters. Later Parker Bros modified this 90 degree angle by machining a radius to this juncture.
A number of the early (square cut) guns suffered cracking at this juncture and the word today is that "If you shoot it often enough, it may crack." Evidence suggests this may be more than just rumor.

The chambers that were cut for metallic cartridges don't crack that we know of. I have a few of these guns and shoot them with the appropriate RST loads and never give it a second thought. If your plastic shell opens beyond the end of the "square" chamber it is no worse than shooting a 2 3/4" shell in a gun with 2 5/8" chambers... maybe an increase of 100 p.s.i.