Without checking I'd assume that's a 2 +3/4 inch chamber. If it's British it might be 2+1/2 inch.
Better have a gunsmith look at if you're not positive. You might get a 3 inch it the chamber
as there has to be space for the crimp to open, but not the crimp on that too long of shell.
Pressures on an old shotgun could be too much.
Oh, and this might help, too.. Shotgun Home Defense Ammunition
Thankyou Jetgirl. I have since edited my PM ! Thankyou for your input, and it was very nice meeting you. What a great place.....almost like work and play at the same time!
Thanks! Hey, by the way...I went ahead and ordered a couple boxes of them. If you don't want any, let me know and I'll take them myself. I'll let you know when they arrive if you want one (or both)...I can always order in more.
I'll let you know when they come in! I can either PM you here when I get home, or if you PM me your phone number I'll call you from the store when they arrive.Thankyou thankyou thankyou!!! for ordering it for me ( I will take both boxes if thats ok with you)
I've got the Remington 870 with an extended mag tube.btw ./..which 20 gauge do you have?
OK. Got my curiosity going, looked up Foster -Thornburg. Seems it died in late 40s
3" magnum born in early 50s... still don't know who made your gun. A British gun would have British
proofmarks.(Google maybe). Personally I'd put 2+3/4 low brass in it and tie it to the bench
and shoot it with a rope...but that's not the best way to check. Find a old gunsmith, they should
be able to check it. Seriously ...don't use the rope trick.