The shell size is normally stamped on the barrel near the reciever. Shells have been made in many sizes over the years ranging from inch & a half mini shells up to three & a half inch magnums. If you cant find a size marked on the shotgun you should have a gunsmith inspect the gun to determine proper size. A shotgun that old cannot fire steel shot. The barrel steel is too soft and will be ruined by steel shot.
NO!!
yes
Can you....I think you mean Can you 'SAFELY' leave shotgun shells in a hot car? The short answer is yes, but it will degrade the quality of the ammo.
If you can't unload it by cycling the action, TAKE IT TO A GUNSMITH!!!!!!!!!!!!
The longest shotgun shell that you can safely use in your 12 gauge shotgun are 3 inchers.
If you are talking about the 7.62x51 and the .308 Winchester then yes they can safely be interchanged
Yes, shorter shells are no problem.
Not safely.
You wouldn't be able to stop safely without them.
Slugs. You CAN shoot lead bird shot in a rifled barrel but it will not give you good or consistant patterns.
I found a great explaination at www.castbullet.com. Easy directions and great pictures. Hope you like it too.
Yes, it can. The Winchester Model 1894/94s manufactured from 1895 through 2006 can all safely handle modern manufactured 30-30 ammo.