How do I figure chamber size?

[levsmith]

Hey everyone, I bought an old shotgun from a local store and its so old I cant find hardly any information on it. All I know is that it was made by J. Stevens Arms and it looks like a copy of the Springfield 1929. Its an Eastern Arms model 1929 16 gauge. Anyways, I dont know how to figure chamber size on it. I have some 2 3/4 shells but I dont want to fire them if they are too long. If anyone could help me out, I would really appreciate it. Sorry if it seems like a dumb question but this is my first shotgun, so go easy on me I've fired plenty of shotguns before but all were marked with chamber size and this one has no markings other than "proof tested 16 gauge". Thanks again for any help.

 

[oneounceload]

Most older 16's were chambered for 2=9/16 inch cartridges, so use 2-1/2. A gunsmith should have the tool to ascertain it exactly.

There are no markings underneath the forearm? Should be something there

 

[levsmith]

Hey thanks for the reply. The only markings underneath the forearm is a letter "B", a 5 digit number under that (I'm guessing a serial number), and a letter "T" under the number.