As a result of the Brownells BRN-PROTO® Retro Rifle project we have a supply of these stripped A1 profile barrels to offer.
At 20 inches in length, this barrel has a 1-12 rate of twist, a rifle length gas system length, and a ½-28 thread pitch on the muzzle, and a .625 gas block diameter. Barrels are magnetic particle inspected. Machined from 4150 chrome moly steel. The gas block journal is shorter than a standard A1, so a standard A1/A2 fixed front sight base will not be compatible. Most low profile gas blocks, with a shorter length will work great.