Been preaching the semi-auto sniper rifle since I was a Lt in the 5th ID in 1985. The M21's problem was it used 1960's tech. The M25/DMR uses 21st century tech. McMillan fiberglass, SS barrels, three point Brookfield/SADLAK mounts ect. Make this system rugged accurate and reliable.
Sniping in combat is more about hitting more priority targets than the 1000 yard one shot kill on the "Field Marshal"
Oh the M24 great Target rifle built for the AMU guru's. Lacking in the combat end of the fight