Issue 32 POF Revolution Iain Harrison POF’s Newest Piston Gun Delivers AR-10 Performance in an AR-15 Package Photos by Kenda Lenseigne With every man and his dog making ARs these days, it takes something rather unusual to make it into the pages of RECOIL. Patriot Ordnance Factory has been teasing the 7.62 NATO Revolution for some time now, and we were given a sneak peek over a year ago while it was in its direct impingement (DI) form. Now that a piston-driven production version has been released, we decided to see if it lived up to the hype. The Revolution’s main claim to fame is that it manages to cram 7.62 performance into a 5.56 form factor. Separate the receivers, and you’ll find that the Revolution upper will drop right onto a Mil-spec mousegun lower. The reverse isn’t true, however, as extra material in the 7.62 lower’s bolt hold open catch prevents a 5.56 upper from seating all the way — we were tempted to break out the Dremel just to prove a point but figured the guys at POF might not appreciate us hacking up their baby for a photo op. Still, the pinholes are in the same locations, relative to both calibers. This similarity in size carries over to the bolt carrier group. While we’ve all gotten used to Armalite and DPMS pattern BCGs having a fatter forward section in order to accommodate a bigger case head, the Revolution’s carrier drops straight into an AR-15 upper. The bolt won’t slide into an AR-15 barrel extension, giving the first clue that POF’s engineers have managed to squeeze every last drop of performance out of the available real estate. These days, we’re blasé that the small frame AR platform can be chambered in some pretty outrageous calibers, but there’s always a limit as to how much horsepower can be wrung out of a cartridge that still fits into its magwell. There’s no getting away from the facts that a 5.56 case head measures 0.378 inch in diameter, and Carpenter 158 steel has a tensile strength of 160,000 psi. Reality imposes finite limits; once you start removing material in order to fit larger shells, you eat way at both bolt lifespan and any safety margin. A x39 or Grendel case is about the widest that can safely slide into the space between the AR-15’s bolt lugs, at a cost of reduced chamber pressure and life expectancy. To expect a 0.473-inch diameter .308 case running at 62,000 psi to function in Stoner’s smaller design is a big ask. Science! To achieve the goal of fitting the larger round into a smaller space, some serious number crunching went on behind the scenes, along with the application of advances in materials science. According to our calipers, bolt lugs were made 10 thousandths of an inch wider and 5 thousandths longer. The area immediately behind the lugs grew in diameter, and a bigger extractor sneaked in, while more material was also added between the lugs. In short, every possible way to add strength back into the bolt was exploited, without increasing the overall size when mated to its barrel extension. Finally, as stronger steel than was available in the 1950s is now a reality, a “super alloy” was selected as the billet from which the bolt would be cut. Which one? Well, we posed that question to POF’s founder, Frank DeSomma who was understandably reticent. “Look, if someone wants to buy my gun and perform spectrographic analysis on the bolt, then I can’t stop them, but I’m not going to hand over that information on a plate. I will say that we’ve tested it down to negative 110 degrees, and had less than 5-percent reduction in strength, which might give a clue.” For the rest of this article, subscribe here: RECOIL Issue 32 Explore RECOILweb:Rainier Arms Introduces CHF BarrelsTrue Grit - Rachel AhtilaGadget Fu: Pakayak - the Ultimate Packable KayakConsiderations for Fighting With a Little One at Your Side NEXT STEP: Download Your Free Target Pack from RECOILFor years, RECOIL magazine has treated its readers to a full-size (sometimes full color!) shooting target tucked into each big issue. Now we've compiled over 50 of our most popular targets into this one digital PDF download. From handgun drills to AR-15 practice, these 50+ targets have you covered. Print off as many as you like (ammo not included). Click here to get IMMEDIATE ACCESS to a digital PDF of this target pack!