I have a M12 in 16 ga that was made in 1928. I have shot maybe a box of shells through it and it is a very fast handling little bird gun w/ it's 26" barrel. I was told recently that I should not shoot it because it may have a 2 1/2" chamber. My shooting it did not appear to damage anything. The chamber length is not marked on the barrel and I've tried to measure it but can't tell for sure. Shooting the 2 3/4" shells didn't seem to hurt it at all. Does anyone know what the chamber length would be on a M12 built in '28 and if it is the shorter chamber, who would you recommend to modify the gun?
Thanks in advance.

I can't recall when they went to the longer chamber, but your gun is right in the approximate time period. If it needs to be lengthened, Mike Orlen in Massachusetts is your man -- excellent work, reasonable price, fast turnaround. I had a 1919-vintage M12 that I got chamber-lengthened. The only sign I saw of the short chamber was that occasionally a piece of the front end of the shell would be broken off when examined after firing.

Brownells sells shotgun chamber legnth gauges at a reasonable price.Their worth it for most of us,then we know for sure. Frank C.

First lets start with the 2 1/2 inch chamber, who ever told you it may be a 2 1/2 inch chamber has no idea what they are talkingabout!!

The first Model 12's were made with a 2 9/16 inch chamber in 16 gauge. If you have a 16 ga. with a 2 1/2 inch chamber it is a very rare gin indeed!!

The chamber length was changed in 1927 to 2 3/4 inch.

Guns that came with 2 1/2 inch chambers were the 20 ga. and 28 ga.

My source of information is "Winchester Shotguns" by Dennis Adler.

Also note that the chamber length is measured from the face of the bolt not from the end of barrel. There is a chamber ring inside of the reciever that is quite thick.

Thanks for the info all. If the chamber length was changed to 2 3/4" in 1927 then all is well because I've verified the date of manufacture to be '28. I really appreciate this site and am glad I found it.

Yep, 2 3/4" it is. I crudely measured from the bolt face to verify then took the gun out and fired / cycled slowly while paying attention to the ejection process. Then I fired / cycled as quickly as I could and the gun performs flawlessly. These ol' guns are like a hammer or a crow bar, they always seem to work.