M1A Accuracy Issues: Bolt Lugs

M1A Accuracy Issues: Bolt Lugs

When installing a new rifle barrel the chamber is 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 do not bear evenly in the receiver locking recesses may wear quickly and set back. 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.

Checking lug fit is best done with the barrel removed so you can clearly see the locking recesses in the receiver where the bolt lugs live. Strip the bolt. Degrease the receiver and the bolt lugs and paint the flat bearing surfaces in the receiver with a marker or Dykem layout fluid.

You will need a tool to apply backward pressure against the bolt face while you work the bolt to rub off the ink and expose the high spots on the contact surfaces. A tool can be fabricated from an old barrel or you can purchase one from Brownells. If you are replacing a barrel with a high round count, the bolt lugs may have seated themselves through simple wear. Most M14 style commercial receivers with low round counts will require lapping.

Original government issue Garands will likely be more consistent, but they should be checked since the bolt you have may not be original to that rifle. Keep in mind that lapping will increase headspace, so it is generally not recommended when reinstalling a used barrel.


M1A and Garand receivers are very hard. You will need a lapping compound containing silicon carbide rather than the more common aluminum oxide or garnet types. Put some compound on the rear of the bolt lugs and install the bolt in the receiver. Install your lapping tool and work the bolt back and forth stopping short of allowing it to unlock.


Remove the tool and the bolt, clean the lugs and check contact as we did above. You will see the shiny bearing surfaces gradually grow wider as you repeat this process. Stop once they are close to 100 percent. We don't want to lap any surface except the flats. Checking lug fit and lapping if necessary should always be done when replacing a barrel or bolt.


Brownell\'s bolt lapping tool

The Brownell\'s bolt lapping tool. Norcross has used this one on dozens of rifles, and says it\'s the right tool for the job to get even lug bearing on both sides.

Lapping tool installed

Here\'s the lapping tool installed. You just insert a punch in the extractor hole to operate the bolt. Rotate it up and down, stopping short of letting it unlock.

The unlapped lug

The unlapped lug at left shows poor contact with the receiver, while the lapped lug at right shows close to 100% contact. Even contact is what you want.

Recommended for You

The Soviet short sword of World War II was the Pistolet Pulyemet Shpagin-1941 (PPSh-41) submachine gun. Rifles

Shooting the Soviet 7.62x25mm PPSh-41 Submachine Gun

David M. Fortier - July 11, 2019

The Soviet short sword of World War II was the Pistolet Pulyemet Shpagin-1941 (PPSh-41)...

Governor Northam is calling a special session of the General Assembly on Tuesday, July 9th, to do nothing but pass more gun control! 2nd Amendment

Virginia Governor Northam Declares War on Gun Owners

Virginia Citizens Defense League - July 09, 2019

Governor Northam is calling a special session of the General Assembly on Tuesday, July 9th, to...

CRKT makes 17 different knife models exclusively for Ruger, from fixed hunting knives to tactical folders, and many of their models are offered in several different styles. Accessories

Ruger CRKT Knives Review

James Tarr - July 08, 2019

CRKT makes 17 different knife models exclusively for Ruger, from fixed hunting knives to...

See More Recommendations

Popular Videos

New addition to the Browning X-Bolt rifle series

New addition to the Browning X-Bolt rifle series

New for 2019 is the Max Long Range model featuring a composite Max stock with fully adjustable comb, spacers for adjusting length of pull, stainless fluted heavy sporter barrel, threaded muzzle brake and extended bolt handle.

New handguns from Smith & Wesson

New handguns from Smith & Wesson

The Performance Center's M&P380 Shield EZ pistol features ported barrel, flat face trigger and tuned action.

Ruger introduces Rifles Chambered in the All-New .350 Legend

Ruger introduces Rifles Chambered in the All-New .350 Legend

Two Ruger American Ranch rifles and the AR-556 MPR are now chambered for Winchester's .350 Legend cartridge.

See more Popular Videos

Trending Stories

This will be the first of many investigative reports about the NRA by Firearms News. 2nd Amendment

Firearms News Investigates the NRA: Part 1

Nedd Scott - July 18, 2019

This will be the first of many investigative reports about the NRA by Firearms News.

If you want to keep the peace, keep and bear arms. Don't give up your guns. Any other choice would be ridiculous. 2nd Amendment

Is Red Dawn Really Just Ridiculous? If Not, Who Would Citizen Disarmament Help?

David Codrea - May 29, 2019

If you want to keep the peace, keep and bear arms. Don't give up your guns. Any other choice...

No one can restore receptivity to another Trump term with these disaffected gun owners but the president himself. 2nd Amendment

2020 is Trump's to Blow with Gun Owners

David Codrea - July 09, 2019

No one can restore receptivity to another Trump term with these disaffected gun owners but the...

See More Stories

More How-To

When installing a new rifle barrel the chamber is cut to optimum headspace. Headspace is the How-To

M1A Accuracy Issues: Bolt Lugs

Gus Norcross - March 08, 2013

When installing a new rifle barrel the chamber is cut to optimum headspace. Headspace is the

Give me a Garand, a pocket full of clips and a place to shoot it, and I'm a happy man. The M1 is How-To

Troubleshooting The M1 Rifle: Bolt Release Timing

Gus Norcross - February 09, 2015

Give me a Garand, a pocket full of clips and a place to shoot it, and I'm a happy man. The M1...

 Jaderborg replaced the Crickett's factory stock with a simple PVC tube with a wooden dowel epoxied How-To

Building a Crickett Rifle for Survival

David Fortier - August 26, 2016

Jaderborg replaced the Crickett's factory stock with a simple PVC tube with a wooden dowel...

See More How-To

GET THE MAGAZINE Subscribe & Save

Temporary Price Reduction.

SUBSCRIBE NOW

Give a Gift   |   Subscriber Services

PREVIEW OUR CURRENT ISSUE

GET THE NEWSLETTER Join the List and Never Miss a Thing.