The 22/50 has been done (Machinist down in Pgh).I’ll bet if you loaded those up with 200 grains of red dot you could win a Darwin Award easy!
Had to go with a smooth bore.......the bullets would spin apart at that velocity (circa '85)..
I'm thinking it was 5300fps? (He built .50 BMG bolt rifles for the ONE MILE crowd)
YIKES!