
Originally Posted by
rob_s
Anyone else ever notice that these threads generally become (or start out as?) nothing more than guys that bought pistons defending their purchases, and guys that haven't bought pistons defending theirs?
My take (copied from an email I sent, some of the below has been argued to death above)...
I am somewhat biased, as I don't see any problems with my DI guns. I'm not "anti-piston", I'm just "anti-piston for me". I have DI guns with 1k+ rounds on them, without cleaning, that haven't had a single malfunction outside of ammo issues. I personally don't think that any of the piston companies have worked out all the bugs, and I don't think that any AR-conversion piston system is going to be as reliable as a DI gun over the long haul. Then there's the whole issue of purchasers as beta-testers, something that I'm not at all interested in. here's the issues as I see it with pistons, and what keeps me from buying one:
1) Carrier tilt. In a DI gun the gas is routed through the carrier and expands inside pushing back against the bolt to unlock the action. This means that it's pushing right along the centerline of the bolt and carrier as the carrier is pushed back into the receiver extension against the buffer and spring. In a piston gun the pressure is on the key, which is off-axis and which causes the tail end of the carrier to tilt down. This means that it rubs, or can rub, on the receiver extension where it meets up with the lower receiver. There have been some reports of pretty extensive wear in this area after only a couple of thousand rounds. AKs and other guns that are designed to run with a piston don't have this problem because the bolt/carrier rides on rails and can't tilt.
2) Proprietary parts. There is no standard for a piston system in an AR. If I need a gas tube for my DI guns I can buy one from any number of manufacturers. If a piston-specific part breaks, it's sole-source and only the OEM maker can supply replacements. This is a problem both in the obvious short term if I need a spare part, and in a future with any potential ban. Is a company who's only product is a potential target for legislation going to survive a ban? and if they go out of business, where do I get that part?
3) Incremental improvement. For the most part, the only thing that the piston makers are addressing is the operating system. I think this is a cop out, although I understand why they are doing it (the quest to get a government contract wherein the purchaser doesn't have to buy a whole new gun but only a new complete upper). If I was going to go with a piston system, I'd like to see other improvements to the overall design of the system (lighter weight, integral rail systems, ambidextrous controls, folding adjustable stock, etc.). Frankly, I'd prefer to see it in a bigger/better caliber like the 6.8 as well, but then you get into ammo cost issues for training.
I consider buying a piston rifle/upper from time to time; 416, LWRCI, XCR, etc. I even shop around looking at what's available. I just can't help getting stuck on the three items above, and none of them would appear to have any resolution in the long term, and certainly are all issues in the short term.
IF the ACR were ever to come out, and IF it was marketed by Remington and IF they can show that they meet or exceed the current milspec for the M4 (or can show why it doesn't apply), then I MIGHT consider a piston operated gun. Maybe.
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