410 - 12mm

Michibay

I have located an older 410 single-shot made by Crescent around 1920 or perhaps older. The barrel says: 410-12mm. I am thinking this is a 410 that takes 2 1/2" shells? I am not sure...I did see a brass 12mm shell on the internet...would appreciate comments...THANKS!!!

Old hickory

More than likely it's 2 1/2 If you have a Fired 2 1/2 shell see if it goes in all the way and you're good to go. The 2 inch 12mm are interchangeable but obsolete since the 1920s.

Mobuck

I saw an old Stevens (I think) marked 12 mm. That particular gun shot 2 1/2" 410 safely.