The Knights Armament M110 is a semi-automatic rifle in service with U.S. military, used as a designated marksman rifle and replaced many M21 and Mk14 systems. The rifle was based on the SR25, which was in turn based on the old AR10 back in the 60's as a direct impingement 7.62x51 semi-automatic rifle. Ammunition used: Black Hills 175gr Match .308 win.
I wonder why the military went with a 1:11 twist rate and not the 1:10 that is usually chosen for those heavier grain match loads.
A 1:11.25 twist is fully adequate for the 175 SMK projectile. Even my old 1:12" barrel will stabilize them just fine. There are other factors in play. For instance, the barrels they use employ 5R rifling, which has different stabilization characteristics. 1:10" twist barrels are great for 175 SMK's, but the extra twist speed over the 1:11.25" barrels is to accommodate for 180gr -210gr projectiles you will find on the commercial market. The 1:11.25" 5R rifled barrels and 175 SMK's are a match made in heaven.
I wonder why the military went with a 1:11 twist rate and not the 1:10 that is usually chosen for those heavier grain match loads.
A 1:11.25 twist is fully adequate for the 175 SMK projectile. Even my old 1:12" barrel will stabilize them just fine. There are other factors in play. For instance, the barrels they use employ 5R rifling, which has different stabilization characteristics. 1:10" twist barrels are great for 175 SMK's, but the extra twist speed over the 1:11.25" barrels is to accommodate for 180gr -210gr projectiles you will find on the commercial market. The 1:11.25" 5R rifled barrels and 175 SMK's are a match made in heaven.