Thank you all for the advice. I will confirm "RB" when I get home this evening, but thanks for deciphering the 1966 proof associated with that code.
I also wonder about the age of these barrels and shooting nitro shells in them, which is my desire. The min walls are .025/.028 which appear to be at the end of the barrel where jug-choked. Elsewhere they measure min .030+. My intentions are to shoot low pressure Nitro and I would appreciate any advice on these intended loads (from an earlier thread) in comparison to comparable BP loads:
12g 2 1/2' and 2 5/8' chambers were proved for a maximum service load of 3 1/4 Dram with 1 1/4 oz. shot. (1220 fps); the "standard" load was 1 1/8 oz. 3 Dram
12g Black Powder pressure
1 1/8 oz. 3 Drams (1200 fps) of DuPont FFFg (82 grains) was about 5000 psi.
1 1/8 oz. 3 Drams Curtis & Harvey’s No. 4, T.S. (82 grains; somewhat similar but not equivalent to medium grain FFg) was about 6500 psi.
RST 12g 2 1/2" shells; fps and psi
Ultra Lite 3/4 oz., 1125, 4400
Falcon Lite 7/8 oz., 1200, 5400
Maxi Lite 1 oz., 1125, 5700
