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AR-15 Bolt Rebuild

It Ain’t Sexy, But Preventive Maintenance Will Keep Your Bad-Ass Rifle Running Strong

Photos by Henry Z. De Kuyper

Warning! When handling firearms, always observe safety rules and the precautions set forth in the firearm’s owner’s guide. Be certain that your firearm is unloaded and made safe before proceeding with this DIY.

After 2,500 rounds or so, the bolt on your AR is probably feeling its age. As part of routine maintenance, you should know how to inspect it, tear it down, and replace any wear items to keep the system running at peak performance. Note that if you ever feel the need to become a hand model, don’t try running an AK at speed before the photo shoot…

Inspecting
To inspect your AR-15 bolt for wear, first remove the complete carrier from the rifle. With the bolt in its forward position, stand the carrier up on a hard surface. If it collapses under its own weight, the gas rings are probably shot. Next, take a small punch or live round and press out on the extractor. There should be significant spring tension. If not, then a bunch of malfunctions are in in your future — addressing problems caused by bad mags, faulty gas rings, and worn-out extractors and springs will take care of the vast majority of all mechanical failures on the AR platform. Finally, while holding the bolt in place, use the same small punch or live round to press down on the ejector. This should have less spring tension than the extractor, but should still feel pretty lively.

1. If your BCG will stand on its end without collapsing, your gas rings are probably GTG.

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2. If it drops to the unlocked position under its own weight, it’s time for a rebuild.

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Stripping
To strip the bolt, remove it from the carrier as you would for normal cleaning. Check the bolt lugs for wear — watch out for rounding of the lugs. Inspect the cam pin hole for any cracks that might be developing; with high round counts, this is an area to keep your eye on. Next, remove the gas rings. These are located in a groove at the end of the bolt and can be peeled out one at a time by lifting up on one end, pushing the tail out of the groove and then running your fingernail around the bolt. Repeat until all three have been removed.

Take a small punch and press out the extractor pin, then remove the extractor from its groove in the bolt. Separate the extractor spring from the extractor, noting which way round the spring goes in the pocket. (Hint: big end toward the extractor). Replace the spring if it did not provide enough tension when you tested it earlier. Inspect the extractor claw for chips or wear — you can drag the extractor on your arm; it should feel sharp and leave a mark. If necessary, discard it and replace with a fresh one.

Place the bolt in a vise and using a roll pin punch, drive out the ejector roll pin. With the punch still in the bolt body, place your hand over the ejector and catch it as you withdraw the punch. Remove the ejector spring. Note that the ejector spring is the same one used in your takedown pin detent, should you ever need an emergency replacement.

3. Check extractor tension by pushing with this convenient tool. They come in handy, spring-loaded boxes of 30.

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4. Press the ejector to check function and spring tension.

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5. The extractor pin should come out easily.

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6. Extractor assembly components.

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7. Lift tail of gas ring up and out of groove.

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8. Repeat two times. Lots of carbon buildup.

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9. Use roll pin punch to remove ejector pin.

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10. Capture the ejector and spring with your thumb; otherwise, prepare to spend time on your knees.

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11. Bolt completely stripped. Now clean that filthy sumbitch.

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12. Check this part of the extractor for wear or damage. If it’s worn, replace it.

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13. Use your punch to compress the ejector spring while you start the roll pin, then drive the pin with the punch.

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14. Replace the extractor spring. Make sure it has the appropriate insert.

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15. Replace extractor and line up pin hole.

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16. Use thumbnail to wind McFarland gas ring onto bolt tail.

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17. Good for another 2,500 rounds at least.

Reassembling
Place a fresh ejector spring into the hole in the bolt face, then drop in the ejector. Be sure to line up the cutout on the ejector body with the hole for its roll pin. Start the roll pin, then press the ejector down while you tap the pin to engage the ejector cutout. Tap the roll pin gently into place and then finish with the roll pin punch. Test that the ejector moves freely.

Place the extractor with its new spring into the groove on the bolt and line up the pin hole. Press the pin into place and test the extractor’s tension.
Wind new gas rings into the groove on the bolt tail using the reverse of the technique you used to remove them. Do not try to force them over the lip — start one end first then roll your thumbnail around the bolt tail. Stagger the gas ring gaps. We decided in this case to upgrade to a McFarland one-piece ring, which eliminates any gaps. Reassemble the bolt into the carrier and test for function.

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