Very interesting. I weighed the "lower" less the magazine of an early hollow HSc (714920) and a later, not hollow "lower" less the magazine (948408), just like the OP. The earlier lower weighted in a 10.4 ounces and the later lower at 11.6 ounces, a difference of 1.2 ounces of material. I wasn't aware there was a weight difference in the variations. I wonder when the internal machining change occurred? I looked at some of my other HScs, still hollow at 818XXX, but not hollow at 905XXX, so somewhere between 818XXX and 905XXX the change occurred. I'm sure other members can pinpoint it more accurately.