Look at 20 gauge slug ammunition.
Look at the ballistics of the hottest factory load you can find.
For instance the Brenneke 1oz 3" runs at about 1500fps.
That's likely about (or maybe even over) what you are talking about for pressure and thrust.
A relatively modern 20 gauge donor gun might just be the thing for you. Maybe not.

Why would the barrel material of the donor gun make a difference for you?
You'd be replacing whatever is on the gun to start anyway.