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You should at least show the carrier of the LWRC system and the proprietary gas blocks used on the A2 versions to compare to the others IMO.
I dont think that a buch of AR180 and AK based weapon actions belong in a thread about piston ARs IMO. Might as well throw custom AKs with AR stocks on the list. ZM Weapons is a DI system, not a piston. |
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Excellent post, very nice to see pics and info on all the systems at once- definitely deserves a tack.
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DevL,
I thank you for your comments. As for the pictures of the LWRC, I do not own one to photo and I could not put every picture I found on the web in this thread. However, if you feel that the gas block or another component that sets it apart from the other manufacturers. Please send me an e-mail or pm and include the photos you feel should appear. As for the inclusion of the Magpul, Robinson Arms, FN, Sig, and Barrett, I was simply attempting to state up front that they were not AR weapons. I hoped this would prevent them from entering discussion later in the thread. As for the ZM, I think it is DI as well but I still can not confirm it. If anyone has any pictures that clearly show the gas system and that the weapon in the picture is in fact a ZM, I would appreciate them. MisterWilson, Per your request, LMT has been added, if anyone has pictures please send them to me. Thank you everyone for your comments |
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Looks like the selector switches don't have to rotate a full 90 degrees to get to one mode. Good idea!
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ZM is an impingement system with the gas key extending to the gas block. The return spring is forward of the upper receiver, under the handguards. The carrier is a standard one shortened so that when fully retracted (at the end of its stroke) it does not protrude beyond the upper receiver. The gas key is taller than standard keys. As a result, the gas tube hole in the upper receiver is located higher. I have a ZM carrier in my parts box awaiting its marriage to a DPMS lo-pro upper and modified gas block.
buckmeister |
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DevL, thanks for the carrier pic. i found some pics of the gas block and added them to the LWRC section.
Which rifle are you talking about? Thanks everyone for your comments |
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Take a close look at the SCAR Colt submissions. |
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Awesome post...I am going piston next build. Screw crapping in my own backyard for now on
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An interesting question that has arisen is whether the bolt carrier scrapes the buffer tube in recoil due to the off axis force impartd by the op rod striking the carrier key.
I have noticed a little scraping in my buffer tube. Someone posted a picture in another thread that had excessive scraping. I was told that LW & HK use carriers that are fatter at teh back end to preclude any potential alignment problems. |
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Did anybody else notice the thread on LWRC’s company owned forum asking if they were having financial problems? The original poster stated they were actually laying off employees. I was watching the thread closely for an official response from the company but instead the thread was trashed very quickly. Nobody has mentioned it sense but that’s not surprising considering it’s a company owned forum so they can do what ever they want. I’m sitting on the fence for a new upper and had been considering them but I don’t want to get stuck buying a product from a company that might be going under.
Does anybody know LWRC current condition? Are they really laying off employees? If so, what does that mean? Will customers be able to still get parts for their guns? - I’m glad I finally registered for an account. I have been reading the forum for almost a year. |
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I have seen that thread as well. I do not know if it is an isolated incident or a problem indicative of the pas piston. Common sense would dictate that the various manufacturers would have considered this in the design and alter the specs of the carrier to compensate. It’s probably one reason that each system comes complete with a proprietary carrier (in addition to the key design). I fired 20 mags through my POF today and did not observe any wear in the tube. I do know that Colt added skies to the bottom rear of its carrier in the 703 project and expanded on it in the SCAR and LE1020. It looks like the LMT thickened the rear of its carrier. When I get some time in the next week I will post some pictures of the different carriers. |
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Thanks for your input but I would not want to speculate on something I do not know. What I do know is that the wait time (I called last week) for an upper is 17 weeks, that’s about the same as POF’s wait time. So I guess we will have to wait and see if anything comes out officially. |
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To clear the air.... No we are not having financial problems. Yes we did dismiss 3 employees. The reason for their dismissal is between us and our former employees. The reason the thread was thrashed on our forum was because of whom started it. Prior to our operators course, we had a number of people (some ar15.com members)through our shop. I'm pretty sure they will attest to our stability and growth. See you guys at "Modern Day Marine" and "Shot Show 08" |
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Interesting - I'd heard things were tight there but didn't know they'd let people go. |
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Thanks Jesse, I think that should clear up the LWRC question.
So has anyone seen or heard anything about the Barrett Gas Piston? I am still looking for information. |
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Is there a thread that discusses the bolt carrier scraping the buffer tube?
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The clinical explanation of buffer tube scraping.
The issue you are dealing with is called carrier tilt. In a standard DI the bolt/carrier work in-line with the bore axis. This changes with an over-head/over the bore piston set-up. Because the op rod in now acting/pushing against the carrier off bore-axis the carrier nose/front will want to lift upward and the ass end will want to tilt downward. We call this carrier tilt or carrier rise. This is what's causing the wear you described. To remedy this problem some manufacturers use simple engineering. First they incorporate a downward slant in the carrier key. If you notice some manufacturers are using a small tomb-stone like striking face on their carriers. This is the root cause of the issue, the linear force being applied off bore-axis. Some manufacturers on the other hand, use a solid key which is dove-tailed into the carrier. This method allows four key benefits 1) Allows them to moves the impact point as far forward as possible 2) Allows then to incorporate the downward slope 3) Allows them to use a material which is designed for high impact loads 5) Allows them to use a shorter and smaller O.D. op rod 4) Allows replacement if needed By moving the point in which the carrier is struck by the op rod as far forward as possible and incorporating the slanted key geometry some manufacturers are able to revector the linear force back to almost bore center-line. The second change to the DI carrier design, some manufacturers engineered a boss onto the end of our carrier. By adding this boss any last bit of carrier tilt in their system is removed, because the tail end is now supported by the buffer tube. LWRC uses this remedy. |
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Maybe this is just me, but if your getting wear on your buffer tube from the carrier than grease that puppy up and keep it greased (or oiled) to prevent and lower that wear. That goes for the buffer tube in deeper, and the buffer and spring too.
This isn't a DI. There isn't a mass of carbon flowing into the receiver that a person should worry about gum-up the same from using grease. That doesn't mean whip out the 1920's axle grease your Grandaddy had stored forever in the basement and was now passed down to you. I like Tetra grease, but there are certainly other good modern gun grease choices out there like XF-7 or Militec. I see more wear from people not lubricating properly or sufficiently than not. |
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Achilles, thanks for the suggestions. I have considered using grease in the buffer tube. I do use Militec on the working parts. I will look into a lithium based grease for the buffer tube.
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That's a sweet looking POF setup. |
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Here is a picture of the gas system from the ZM Weapons AR: ETA The abreviated carrier allows the buffer tube to be eliminated and replaced with a folding stock, but (as far as I can tell) would not work with |
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Very interesting thread comparing the different gas piston systems.
Thank you for the informative post. |
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I have a LWRC M6A2 upper and it too has some wear on the bottom of the buffer tube. However, it is more of a smooth, beveled wear (if there is such a thing) as opposed to gouges like were shown in the pics of the POF. It hasn't affected function so far. I just hope it's the kind of thing that only wears so far then is good to go and not the kind that will continue to dig down indefinitely.
ETA---my LWRC upper is on a Bushy lower so the buffer tube is not of LWRC design (if indeed their's is any different to accomodate this issue). |
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