I load and shoot 32 S&W long for 4 Colt Police Positive and Police Positive Special revolvers spanning from 1923 to 1955. My load is a Lee 93 gr. cast from 50/50 WW/PB, air cooled and sized to .313, lubed, they weigh 95 gr. consistently. Over 2.5 gr. Bullseye in Remington cases with any SP primer. Excellent performance for years.
Recently I acquired a S&W model 31-1, good shape and very smooth. My problem is: I am splitting a case every once in a while in the Smith. I marked the chambers to try and I.D. a problem chamber, all of them will split a case from time to time. I have cleaned and measured the chambers, bore is clean, but 5 groove rifling I can't measure accurately with my home tools. What diameter did S&W use in these bores, its an early 70's gun, 50 years newer than some of my Colts and 20 years newer than my newest Colt.
Does anyone have any ideas what is going on? I'm stumped, I don't want to have a special load for a problem child, I'll sell the S&W before I go that far for plinking.