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Thread: Piston or Gas?

  1. #81
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    Eh, I have no dog in the fight either way. I have DI uppers aplenty in 5.56 and 6.5 and exactly one PWS .223 piston upper I'm writing an article on. I'm at 1930+/-rds since the week before SHOT and not a single failure that wasn't attributable to ammo or me (excepting a buffer detent failed). I gave the bcg 2 small squirts of MPT lube when I got it and nothing since except to use compressed air to blow off the exterior dust from a really bad day at the range in February.



    There are two tiny marks on the receiver extension, about 2mm wide by 1mm long (no depth that I can feel) caused by sidewall loading (the actual term for 'carrier tilt').
    I'm enjoying mine so far.
    Last edited by KellyTTE; 04-27-09 at 03:12.
    Kelly H
    Yes, I know. No, I won't tell you.

  2. #82
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    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.

  3. #83
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    Yeah i never intended to have this thread turned into somthing from TOS I just wanted advice, which i got so its over. Thanks for giving me your opinions ill take them for what there worth and buy a DI for my first upper and will see what the future brings beyond that. I think ill stick with my first piston gun, my AK
    "Calling an illegal alien an undocumented immigrant is like calling a drug dealer an unlicensed pharmacist"

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  4. #84
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    flynn, you bring up a good point. Frankly, if I were bound and determined to have a piston-operated 5.56, I'd try to track down an AK in that caliber.

  5. #85
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    Quote Originally Posted by rob_s View Post
    flynn, you bring up a good point. Frankly, if I were bound and determined to have a piston-operated 5.56, I'd try to track down an AK in that caliber.
    I was more just looking at other AR options really, im quite content with the punch of the 7.62 as opposed to the 5.56. I think the AK was made for the 7.62 and the AR for the 5.56. Although it would be interesting to have the ruggedness of the AK action in a 5.56, but those are probably few and far between id guess. I was just entertained by the fact that theres a piston AR i wasnt really dead set on a piston or DI im just happy to be able to build one
    "Calling an illegal alien an undocumented immigrant is like calling a drug dealer an unlicensed pharmacist"

    If you can't get behind our troops feel free to stand in front of them

  6. #86
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    Quote Originally Posted by rob_s View Post
    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.

    Rob,
    Dont get me wrong, I respect you and you have a good reputation. I am definitely not challenging you...
    But, Cant it just be that people are sharing their experiences and proud/happy that they're not experiencing some of the other issues that many people talk about???
    I dont even share my experiences anymore, the reason being, is I'll get dubbed and thrown into a gaggle of people who are just trying to fool themselves into believing they have made a good purchase.
    Alot of people around here dont carry your level of merit, your well respected, I see it a little unfair to point out people who might just be wanting to share some info and happy to do so, as they see others with high merit doing the same...

    Again, I respect you and Im not trying to challenge you. Just sharing my concern.
    Please accept it for what it is and do not take offense. I have seen what your talking about, in more than just piston gun threads. Rail systems, stocks, triggers, etc... etc... Not everyone is humble in their postings and if thats where your coming from, then I understand.
    Thanks Rob,
    Seth H.

  7. #87
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    No offense taken, and you're absolutely right. People who are reading threads like these, whether about pistons, stocks, or ball-gags, need to take into account the people that are doing the talking. Regardless of the product being discussed, people tend to defend their purchases to the death (look at any thread discussing the Chart as an example) because they think it reflects on their ability to rationally make a decision.

    The other issue is that quite a lot of people that share their experiences and opinions fail to properly qualify those opinions. Having a "flawless piston gun" is kind of a useless statement if it only sees 200 rounds per year and the shooter has zero experience with a quality DI gun.

    The other side of the piston argument that I see a lot is shooters that argue in the exact same post that they "need" the extra reliability of their piston gun but that they didn't "need" a Colt when they bought their DI gun because their Bushmaster ran "flawlessly" for 10k rounds. I'm still at a loss as to what these shooters were then improving on.

    Ultimately people have to make informed decisions for themselves. That's why I posted the three bullet points that I did. They are the things that hold me back from buying a piston gun and they are things that I don't see really getting addressed in the market/industry. As long as a potential buyer doesn't care about being an early adopter of a gun that they may or may not be able to get parts for next year (or even tomorrow) with an incremental (at best) improvement to the operating system; that's my only goal with even bothering to post in this thread.

    I see it a little unfair to point out people who might just be wanting to share some info and happy to do so, as they see others with high merit doing the same...
    I would never tell someone not to share their experiences or opinions, as long as they qualify those experiences and opinions at the same time.

  8. #88
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    Okay, fair enough.
    Thanks,
    Seth H.

  9. #89
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    Quote Originally Posted by dmanflynn View Post
    I was more just looking at other AR options really, im quite content with the punch of the 7.62 as opposed to the 5.56. I think the AK was made for the 7.62 and the AR for the 5.56. Although it would be interesting to have the ruggedness of the AK action in a 5.56, but those are probably few and far between id guess. I was just entertained by the fact that theres a piston AR i wasnt really dead set on a piston or DI im just happy to be able to build one

    Flynn,

    I bought my first AR last year. I did a whole lot of research before purchasing it (at least as much as I could on my own). I ended up getting the LMT MRP CQB Piston version. It was a new platform brought out by LMT.

    Now LMT had been testing it's prototype for almost two years before releasing it. They shot thousands of rounds of ammo through it.......full auto, suppressed, and of course for accuracy. More importantly, at least for me, was the fact that LMT designed their piston rifle on their MRP CQB platform so that anyone that wished to could revert back to DI without any problems what so ever!!!

    Again, this purchase was my FIRST AR rifle and so far my only AR. I'm completely satisfied with it even though I did have to send the upper back to LMT the first time I took it out shooting. It had intermittent short stroking. After contacting LMT, Gene Swanson (their testing/CS guy) told me about their gas port size being minimum and wouldn't function with all 223/5.56 ammo. He took care of my problem withing a week and I've not looked back since.

    It's your choice and if it's your first AR (build or purchase); look, listen, and most importantly do your own research before getting one. The 'Piston' craze really started a few years ago and comparing it to the DI version of the AR is a little unfair. Yes, piston AR testing prior to a few years ago was done, but not to the level of engineering and research that has been done in the last few years! Remember, when the AR first came out, they had problems that had to be worked through. Never mind what they were; it was new and it did have problems. They were worked through and we now have a platform that we 'know' real well. We have been using this DI platform for over 40 years and if the quirks hadn't been worked through, I'm sure that the military would have dumped it a long time ago.

    As I see it, the use of the DI AR rifle is a PROVEN platform PERIOD!!! I CHOSE to get the LMT Piston rifle. My uses are purely recreational. I don't RELY on it for anything other than fun. I hope to hunt with it in the future, which again, is recreational in nature. If I were REQUIRED to use one for me or my families protection, ie. THE ONE and ONLY gun in my house or patrol car, I would CHOOSE the DI version. That said, since I am not REQUIRED TO or HAVE to RELY on it for personal/family protection, AND it was MY choice, I chose the LMT platform. Like I said earlier, if in the future LMT goes belly up, I can always return it back to DI or just change uppers. Remember, it is after all the COMMON 'AR' platform that can support everything from SBRs, suppressed, LR shooting, hunting, plinking, caliber changes, and yes PISTON uppers!!!
    God Bless and good shootin'!!!

  10. #90
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    I've had a piston AR since 1987 and it works great!!! And I paid less than $325 for the whole rifle!!!! NEW!!!



    A Flattop K2 with a railed fore end, an adjustable stock, accepts AR P-grips and a 90 degree selector would be near-perfect.

    If i were rich, I would make an improved version of this rifle and call it a day.
    Last edited by Heavy Metal; 05-02-09 at 17:42.
    My brother saw Deliverance and bought a Bow. I saw Deliverance and bought an AR-15.

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