I was fortunate to aquire a S&W 16-4 revolver. The cylinder throats measure .311, verifyed with pin gauges. I slugged the barrel, and although it is 5 groove rifling, I extrapolated the groove diameter, to between .3125, and .313. I shot 30 Speer 98 gr HBWC bullets, with 1.9 gr Bullseye, out of it, leaving light leading at the first 1/2" of the barrel. It shot pretty decent. Half dollar sized groups at 50 ft from a crude rest. Granted, it was only 30 rounds, as I didn't have anymore to try. Possibly after 100 rounds, the result might be different.
Possibly the HBWC bullets were swaged down, and due the the HB, expanding up again to groove diameter. I had ideas of using a chucking reamer of .313, and putting a fired case in the cylinder to act as a pilot, while protecting the cylinder walls, or getting a 5/16" brass lap, and open it up that way. Any opinions or ideas on this situation.
