Gunsmithing
Battle Rifle Maintenance
Lapping Semi-Auto Lugs
Wednesday, 08 September 2010
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The Brownell's tool screws in to the front of the receiver and applies pressure to the bolt face. Models are available for bolt-action rifles as well as the M1 and M14. (Photo: Gus Norcross)
When installing a new rifle barrel, the chamber's cut to optimum headspace. Headspace is the distance from the bolt face to a datum point on the shoulder of the cartridge.

Bolt lugs that don't bear evenly in the receiver locking recesses may wear quickly and set back, thus opening up this critical dimension. Accuracy and smoothness of operation may also be degraded.

Lapping lugs is a common practice when tuning bolt guns, so what about semi-auto battle rifles like the M1A and M1 Garand? Same concept.
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