They may have made it with a 2.5" chamber, but it may also have been opened up later to a 2.75" chamber. One way to check is to drop a 2.75"dummy shell inside the chamber, if it doesn't drop right in then it absolutely is a 2.5". If it DOES drop in that doesn't mean it's a 2.75", as the mouth of the dummy might compress, and the edge of the chamber isn't going to be square like the lip that holds a .45 ACP cartridge in a 1911 barrel.
Take a spent 2.75" shell, and insert it into the chamber, and make sure the slide will go into battery. Then cycle the slide and see if the extended once crimped edge of the shell will clear and allow the shell to be ejected clean. If the front edge of the shell hits the chamber opening and doesn't cleanly eject, it again may be a 2.5". The only sure way to tell is to take it to a smith.
LD
