The claim is 2630 FPS for a 108 gr. from 18":
The combination of the proven REC7 DI gas system and the potent 6mm ARC cartridge creates a consistent, accurate cartridge, according to Barrett. It carries 24 round in the magazine. Meanwhile 108-grain ELD Match bullets exit an 18-inch Proof Research barrel at more than 2,630 fps. It also delivers supersonic capabilities past 1,000 yards.
I'm thinking a 20" barrel might be about right...
