in a single shot shotgun chambered for 3" would it be safe to shoot 2-3/4" shells through it or not? just curious. i have never worried about it, i have a 12 super mag remington, but am looking at a new shotgun.

Sure....no problem.....shoot away! Regards, Rick.

so i can shoot 2-3/4" and 3" in an encore shotgun barrel, but not over it right?

A 3"chambermeans that you can shoot ammunition up to 3" in the gun.