May 8th, 2010

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.

McFarland 1-piece AR15 bolt gas ring

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, 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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