M1 Garand HRA Bolt 6528287 HRA .U. Stripped 4.74 mil on useM1 Garand HRA Bolt. Bolts are stripped and marked 6528287 HRA with .U. (for Underwood manufacture). 6528287 bolts are proper for HRA's in the 4.74 thru end of production serial number range. Bolts have been refinished and excellent. Several available, select quantity needed when ordering. Sample from lot pictured, all similar condition.