Tech Tip: Fit One-Piece McFarland™ Gas Rings in Your AR
If you use an AR-platform rifle for varminting, multi-gun matches, or Service Rifle competition, one simple upgrade you can make to enhance reliability is to replace the mil-spec gas rings with a one-piece McFarland™ bolt gas ring. The McFarland ring is a single spiral of spring steel that loops around the bolt three times and leaves no path for gas leakage. With conventional gas rings, you need to correctly rotate each ring so the “gap” does not line up, thereby allowing gas blow-by that can cause cycling problems. The one-piece ring is an inexpensive, “set and forget” solution that eliminates the need to monitor your ring position on the bolt body.
The one-piece McFarland gas ring is recommended by Fulton Armory and other AR experts. Installation is simple and the one-piece rings last a very long time. One AR user comments: “Ever since I tried single rings I would never change back to mil-spec rings. I’ve experienced more consistent recoils and cyclic rates of fire. And, as to wear — I haven’t worn one out yet.” On Brownells.com, two gunsmiths offered these reviews:
“Easy install, zero chance of a gap, one less thing to worry about in the bolt carrier group. This item should greatly improve gas pressure consistency. This is a ‘must have’ item.” — Jake, SC
“The concept is simple and sound. The one-piece gas ring removes the possibility of gaps lining up. It installs easily, holds great tension, and is cheap. Doesn’t get much better.” — Lane, TN
The McFarland™ one-piece bolt gas ring can be purchased from Brownells for $3.99 (item 100-001-257) or from Fulton Armory for $2.99 (item FA-AR-300-109). Purchase three or four at once to save on shipping costs — that should be enough for a decade of AR shooting.
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Tags: AR15, Bolt, Gas Gun, Gunsmithing
These gas rings are an excellent change over the conventional 3 piece. After firing a NRA HiPower or CMP match, would clean the rifle & rotate the 3 rings so the gaps were 120 degrees apart. Fire the next match, and when cleaning always found 2 gaps lined up with the third one very close. Installed the McFarland’s in all 3 uppers, end of problem!
Tried these in 2 different guns, only lasted 200 rounds before wearing out. Standard DPMS rings now on 800 rounds and still working. Dont waste the money.
to Bre25–
My experience, with 4 different AR uppers using one-piece gas rings, is 100% opposite to yours. The one-piece rings worked perfect and there have been no wear issues after literally thousands of rounds.
I do apply a heat-resistant lube through the bolt-carrier hole and I keep my bolts very clean and remove excess carbon build-up inside the bolt body.
It has also been suggested that wear can be accelerated if the bolts or carriers are slightly off specs. My uppers all use genuine Colt bolts and bolt carriers.
Otherwise there is really no reason why the one-piece rings should wear faster than conventional AR bolt gas rings. If anything, they should last longer — and that seems to be the experience of most users.
Both were Young national match bolt carriers, spoke to Dan Young about it and he confirmed I was not the only one. Yes they were properly lubed
Aha… we may have something. The Young National Match bolt carriers are chrome-plated (at least as shown on http://www.youngmanufacturing.net). It is certainly possible that the McFarland ring might behave differently in a hard-chrome-plated carrier which may have tighter tolerances and different surface properties. That’s worth noting.
I am reminded of the fact that way back in the early days of the M16, the government specified chrome-plated bolt carriers, then abandoned the idea because the chrome carriers wore out the uppers at an accelerated rate. Here’s one comment: “External chroming on your carrier is both unnecessary, and detrimental to life of your upper receiver. Strips thru/wears dry film lube, breaks thru residual CLP. Uncle Sugar found accelerated wear patterns in uppers in the mid 1960s and pulled the chromed carriers for these reasons.”
My experience with the McFarlands mirror’s that of the editor. My Colt H-Bar upper, bought new in 1995, and now on it’s third barrel, (original Colt, and 2 Kriegers), 10,135 documented rounds fired, same Mcfarland ring, since 1997. Use nothing but Breakfree. Two Bushmaster upper’s each with 5 & 7800 rds. fired, same McFarland rings.
>With conventional gas rings, you need to correctly rotate each ring so the “gap” does not line up, thereby allowing gas blow-by that can cause cycling problems.
I wonder how this legend this lives
I´ve never ever heard of anyone with gas ring alignment problem IF the rings have been intact.
A friend of mine bought a new custom AR with regular bolt with McFarland rings + JP lightened steel carrier. The gun did not cycle properly. After replacing McFarland rings with regular rings the gun worked ok. Dunno what was wrong with those rings.
Firing tens of thousands of rounds in High Power comp, using several different uppers, not one alibi using the mil-spec, 3 piece, gas rings. I don’t pay any special attention to the gap alignment when cleaning/reassembling.
Steve,
Thanks for the feedback. I have seen the split rings cause a problem in 16″ barreled rifles shooting milsurp ammo with sustained rapid fire (meaning multiple 20-rd or 30-rd magazines shot quickly.)
Obviously, however, if the mil-spec rings work 100% for your use, one-piece rings may not be advantageous.
How do you install the 1 piece gas ring?
Dom you have to peel the edge of the one piece off and guide it into the channel and then rotate it around and around while keeping pressure on the ring it will wind right into the channel.
I have a failzero bolt and this one piece design is very very tight and has me a bit concerned about firing it like this.
My pistol 7.5″ barrel upper continually seems to realign all three gas rings so that gaps align. After even just one magazine! Then the empty brass fails to eject and I have a double feed. I can’t wait to try this one piece.