Turns out after taking this rifle to the range, I couldn't get any 140 grain or larger loaded cartridges to chamber. I tried chambering a new W-W empty and the bolt closed on it with no resistance. The rifle must be throated for a particular load, probably 120 grain bullets. No 120 grain factory 7x57 load was available in 1950, or now for that matter, so the owner must have been a handloader. Not sure about the rate of twist, either. Sandlapper