I recommend against using direct impingement with a round that appears to have the same dimensions as 8 x 57 mm Mauser. That is a very powerful rifle round that puts a lot of fouling on the bolt face (a lot more powder in the cartridge), and also produces a lot higher peak pressure.
Despite what a lot of AR devotees will tell you, using a short-stroke piston is not going to degrade the rifle's accuracy by any meaningful amount, and the recoil will be reduced to moderate (instead of moderate to heavy).
DI is better for a small cartridge, such as 5.56 mm.
Also, 2,800 m/s is blindingly fast. Unless the rounds are being propelled with something other than chemical reactions, this needs to be reduced. You're looking at something probably around 1,000 m/s (~3,200 fps).