You know, I love this guy. There’s no double talk and absolutely no praising up a crappy gun because he gets paid to write an article. I’ve felt this same way on Gas Piston AR-15’s but the public loves them. Why? Allow me to explain. There has been some horribly out of spec AR’s out there. What I mean by that is this. Every firearm blueprint has a tolerance variance. It will have the exact measurements drawn out and will allow for “+ or – .0010” for example. Now the gun will function fine as long as you stay to that tolerance. Go outside that and you have a poorly (if at all) functioning gun. To fix that problem (that they created by not having better quality control) they introduced the piston upper. Now that you know the truth let’s hear Mr. Farnam’s experience with them was.
14 Apr 09 Gas-piston Stoner Rifles: I just completed an Urban Rifle Course in UT. Students brought the usual assortment of AR-15s and Kalashnikovs. We also had one RA/XCR (mine) and one DSA/FAL. All ran fine for the duration, except for one of the AR-15s, which was a gas-piston model. All the other ARs were conventional Stoner System (pressurized receiver) models, and all experienced no more than the usual number of hiccups. However, the one gas-piston ARs displayed many unscheduled interruptions, mostly failures to eject. We all made a mental note that this is not a rifle any of us would want! Unhappily, this experience has been typical at our UR Courses. As a rule, gas-piston ARs do not hold up nearly as well as conventional ARs. To add insult to injury, gas-piston ARs are a good deal more expensive than are standard models! It strikes me that, in their enthusiasm to maintain the classic AR-15 profile, designers attempting to equip this rifle with a gas-piston have produced both a piston and op-rod that are tiny when compared with those found on the XCR, SIG/556, and other military rifles in the same 223 caliber. Apparently, a gas-piston system that small is below the reliability threshold, because we can’t seem to keep them running satisfactorily. The original Stoner System (pressurized receiver) has had a disappointing tenure. Compared with gas-piston systems, like the Kalashnikov, it has been excessively maintenance-dependant, because so much garbage ends up in the receiver. Gas-piston rifles don’t get nearly as dirty, nearly as fast. However, in my opinion, gas-pistons and op-rods must be substantial, even on rifles chambered for 223. Tiny parts and tiny systems do not reliable rifles make!