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2/23/2017 5:55:53 PM
Posted: 12/7/2011 6:22:13 AM EST
Why are there two holes in the bolt carrier- the ones visible through the ejection port? Are they lubrication points for the bolt? I have not seen them mentioned in the AR lube diagram.
Link Posted: 12/7/2011 6:24:08 AM EST
They vent gas.
Link Posted: 12/7/2011 6:33:54 AM EST
Originally Posted By 0612Devil:
They vent gas.


Yes.

You could lube them, but it will just blow the lube out on the first shot.
Link Posted: 12/7/2011 6:40:42 AM EST
When not field stripping the weapon, but lubing up in the field, I usually retrach the charging handle about a half-inch until the gas rings show through the holes in the carrier.

I then put a couple of drops on the bolt lugs as through the holes on to the gas rings.

~Augee
Link Posted: 12/7/2011 8:35:01 AM EST
Those two holes are the exhaust ports for the gas system. After the bolt carrier moves to the rear and unlocks the bolt, the gas rings move forward of those holes and the gas contained within exits out those holes and out the ejection port.
Link Posted: 12/7/2011 8:41:30 AM EST
It is a good way to introduce lube into the system though "on the fly" Just pull the charging hand back until the bolt unlocks then drop a few drops into those holes. It'll keep a dry gun running for a little while longer.
Link Posted: 12/7/2011 10:49:02 AM EST
Gas vents, part of the gas system that unlocks the bolt out of battery after a round has been discharged.
Link Posted: 12/7/2011 11:53:45 AM EST
Originally Posted By Augee:
When not field stripping the weapon, but lubing up in the field, I usually retrach the charging handle about a half-inch until the gas rings show through the holes in the carrier.

I then put a couple of drops on the bolt lugs as through the holes on to the gas rings.

~Augee


This.....
Link Posted: 12/7/2011 3:53:38 PM EST
If you watch the ultra slo-mo vids of ARs firing and ejecting you will see gas venting from those holes.
Link Posted: 12/8/2011 7:43:14 AM EST
Originally Posted By Augee:
When not field stripping the weapon, but lubing up in the field, I usually retrach the charging handle about a half-inch until the gas rings show through the holes in the carrier.

I then put a couple of drops through the holes onto the gas rings and then on the bolt lugs as well.
~Augee


Edited for clarity. Good tip by the way!
Link Posted: 12/8/2011 4:34:16 PM EST
Vent un-needed gas. Also a lube point for the piston rings. Squirt in there with bolt in battery and slightly out of battery.
Link Posted: 12/8/2011 4:48:56 PM EST
Originally Posted By Ohio_Bill:
If you watch the ultra slo-mo vids of ARs firing and ejecting you will see gas venting from those holes.


Yep. Those two holes are simply the gun's exhaust pipe.
As the bolt carrier begins it's rearward motion, and just before the carrier key pulls away from the gas tube, the gas rings on
the bolt pass to the front of those holes, allowing the gas to escape to the outside of the receiver.
If those holes weren't there the gas would be vented inside the receiver as the carrier key left the gas tube, dumping all that carbon and fouling into the receiver.
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