A hot 280ai is a mild 7mag either one there's not a critter alive that will take one thru the lungs without getting pretty sick.

Yes you can shoot factory 280 to collect your fire formed brass.
If I don't go 338-06 with my CLR build I'll be going 280AI and you can give it a run when it gets back.

Want To Buy;
Form die for a 7mm Mashburn Super.
.284 Hornady AMax 162gr.
.224 Hornady AMax 75gr.
22-250 bushing die
Bushing die that will work with the 7mm Mashburn Super
A couple Glock 42 380ACP mags