In the early 20's the standard 12 gauge chamber was 2 5/8". Not exactly sure the exact date or even year, I have read/heard 1922, 1924, etc. I do know that the 3" magnum came out in 24, but not certain if the 2 3/4" chamber was made standard at the same time, I've read and heard that too.
It wasn't necessarily that the forcing cone was "cut" for roll crimps. 2 3/4" shells made with roll crimps "fit" a little better in a 2 5/8" chamber...but that is not a good way to conclude the chamber length or whether or not it has an extended forcing cone. Easiest way to check for an extended forcing cone is to look in the breech. You wont have any trouble seeing it if it was cut and lengthened. Best thing to do, since your gun dates to the time it could be 2 5/8" is to take it to a smith and have it lengthened.
You could also try removing the barrel and taking a photo looking into the breech as best you can and post it. If it is clear at all I can tell you if it was cut with a lengthening reamer. Definitely have it checked though and don't shoot any slugs until you know. It's really not a good idea to shoot any 2 3/4" shells because they will produce more pressure and recoil and beat the gun up. I have seen several cracked stocks on older shotguns due to this. Best to have it lengthened anyway...this helps to further reduce recoil and can improve your pattern.
Edit: sorry, to answer your question directly...no, the fact that the crimp is not "torn" or otherwise showing any damage is NOT the okay to go ahead and shoot whatever you want in it!!! Have it checked for certain. FWIW, prior to the 2 3/4" standard chamber the 12 ga was 2 5/8", the 16 was 2 9/16" and the 20 was 2 1/2"
Last edited by msinc; 06/01/23.
