I recently switched out the front sight on a BM 16" superlight barrel to a PRI folddown and the rifle started short stroking during the subsequent test fire. When I removed the PRI sight I noticed that the gas port in the barrel is drilled about 0.060" off center, restricting gas flow into the PRI. Two of the other four 16" BM barrels I checked had the same problem.
Is this a common problem for Bushmaster??