A finish reamer designed to remove the last few thousandths from a "short chambered" barrel to properly headspace the rifle. The reamer is inserted into the chamber, allowing the bolt to push on the back of the reamer. A drive rod is threaded into the reamer, inserted from the muzzle and turned from the muzzle end. Finish ream the chamber until the bolt lugs drop-in for perfect headspace.
Insert the reamer into the pre or short chamber. Make sure the bushing is on the end of the reamer then screw the drive rod into the pilot of the headspace cutter after carefully slipping the drive rod down the barrel. Rotate the cutter with foreward pressure applied to the bolt. Once the bolt rolls over and locks, clean the chamber and check headspace.
Base-to-shoulder length is minimum spec. If the headspace reamer is used properly the headspace in the rifle will fall within .001 inches of minimum.
It is important to check headspace as soon as the bolt is fully locked. If you continue turning the cutter after the bolt locks the bolt return spring will continue to apply forward pressure on the cutter and cause it to cut until the bolt lugs bottom on the front of the bolt lug recess. This will result in excess headspace.
Caution: The reamer pilot is drilled and tapped for the drive rod so be careful not to apply excessive torque. Some barrels may have small bores and it may be necessary to grind pilots down. The standard thrust bushing thickness is .250".
NOTE: Drive rods may exhibit slight surface rust. This in no way affects the performance of the reamer itself. It is recommended that drive rods be wiped down with a light oil prior to use.
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