Helical McFarland Style One Piece Gas Ring for AR-15 Bolt AR15 by Luth-AR
Reassembling an AR-10 involves aligning the gaps in the gas rings to make sure they are as far apart as possible. We do this to avoid all sorts of problems and malfunctions and the standard rings need to be replaced about every 3000 rounds. Finally, there's a solution that permanently eliminates the need to adjust the rings' alignment, and lessens the chance of jamming.
Break In Note: MADE IN THE USA. CORRECT SIZED AUTHENTIC MCFARLANDS ACTUALLY CREATE MORE FRICTION WHEN NEW AND RUN A BIT TIGHT WHEN NEW. I TYPICALLY OVER LUBE WITH MOBIL-1 AND WORK THE BOLT BACK AND FORTH ABOUT 50 TIMES, CLEAN THE CARRIER AND REPEAT A FEW TIMES UNTIL THE OIL STOPS LOOKING GREY AND DIRTY. THIS POLISHING IS ALL THE BREAK IN I'VE NEEDED. RECOMMENDED BREAK IN IS 250 ROUNDS AND THESE RINGS LAST AT LEAST 10,000 ROUNDS. THEY HAVE BEEN FLAWLESS FOR ME AND I'VE HAD NO COMPLAINTS OTHER THAN THEY ARE STIFF INITIALLY.
How It's Supposed To Work
Upon firing, as the pressure of the gas generated by the burning propellant drives the projectile down the barrel and past the gas port, a small quantity of the gas is bled off through the gas port, gas tube, and bolt carrier key into the cylindrical section in the bolt carrier where it expands and drives the bolt carrier rearward. During the first rearward travel of the carrier, the bolt is rotated by the cam pin acted on by the bolt carrier cam slot. This rotation disengages the bolt lugs from the barrel extension lugs and so the bolt is unlocked. The carrier then continues rearward with the unlocked bolt. At this point, the gas used to drive the bolt carrier rearward is allowed to bleed out through two holes on the right of the bolt carrier.
The Problem
In order to install the rings on the bolt, they must be split and thus a "gap" on each ring is unavoidable. The problem arises because these gaps can become aligned, and cause too much gas to escape too early in the cycle. This can result in short-stroking and possibly jamming the rifle, so manuals and instructors enforce the proper alignment of the rings when reassembling the AR-10 rifle.
The Solution
The McFarland one-piece gas rings solves the problem of "aligned" gaps by eliminating the gaps. As a one-piece helical ring, you are guaranteed to never have the problem with the gaps.
Replacement
The 3 individual rings can be removed one at a time starting with the rearmost ring first. Lift one end of the open ring up and over the edge of the ring groove (towards the rear of the bolt) and then work the other end over. Repeat this for the remaining two rings, and you should be able to remove them without damage. As a single piece of metal, the McFarland ring is wound onto the groove on the bolt's rear. Start one end over the edge, and then work the remainder of the ring over that edge; the easiest way to accomplish this is without trying to turn the ring itself.
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