I picked up an Aries Defense piston conversion kit for one of my AR carbines last week. I did a bit of reading on them as I always wanted a piston upper but didn't want to spend an arm and a leg (and a testicle) to get one. I've shot the POF and wasn't all that impressed. The recoil impulse is terrible as it causes excessive muzzle climb and the system itself is pretty heavy. Also there is no retrofit for an existing system, it can only be purchased as a complete upper...and it's pretty damn heavy. The GSR-35 kit can be installed in less than 10 minutes, is totally reversible, and weighs a total of 4 ounces more than the parts that get replaced. The kit includes a gas spigot, piston cup, operating rod, op rod spring, op rod bushing, machined bolt carrier and a set of modified double lined M4 handguards. Installation entails removing the gas tube pin, removing the gas tube and stripping the carrier of the bolt, cam pin, firing pin & firing pin retaining pin. Assemble the bolt & parts on the new carrier, install the op rod bushing inside the upper receiver (where the gas tube goes through the upper), op rod & spring, gas spigot and then gas cup. I've ran 12 mags through and noted some excellent positives. First off, the upper remains clean...no carbon or crud at all. Also the bolt tail isn't caked with carbon. The bolt & carrier remains cool even after running 3 magazines back to back. I shot the mags and immediately pulled out the carrier and it was as cold as it was before shooting the first shot. It was also very clean and still had the lube that I put on before the range session. Recoil impulse was the same as with the regular DI system. The piston system is low mass & short stroke. I'm working up an in-depth review with many pictures & some youtube video of the conversion in action. The kit MSRP's for 399.95, but Ares offers a military & LEO discount for 359.95
