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Thread: Geissele / Light Alum Rails Unreliable? Per Internet...

  1. #1

    Geissele / Light Alum Rails Unreliable? Per Internet...

    I bought my first geissele rail, an MK16 rail this week and I liked it so much in hand, uninstalled, that I went to buy another but it was sold out from the one dealer who happened to have them 2 weeks ago in the size and color I wanted.

    So I googled around more and found a trove of internet hatred for them, and not just them, but potentially any light free float alum rail system that hugs the barrel tightly. ]

    Allegedly, the us military or someone did drop testing and when they dropped these URGI mk16 rails, the rails bent slightly, contacting the gas block which is really close to the inside of the rail, and changing point of impact by something ridiculous like 5 To 10 MOA.

    Then apparently according to a Reddit summary of the issue, this was all over ARFcom 2 years ago and was wiped by moderators who, depending on your standpoint, were either trying to cover it up. Or they were getting d0xing/death threats from Bill geissele off their forum.

    Personally I don’t put much stock in arfcom or Reddit, but it does seem very plausible a drop of the rifle could bend the rail every so slightly and cause it to press against the gas block, so internet rhetoric aside, before I buy a few more of these for different uppers I want to make sure it’s not an issue. By asking here, with reasonable common sense folks.

    I’m wondering if I shouldn’t stick with a heavier and more durable 4-way pic rail setup for an upper I plan to run an IR laser on, since it seems like the issue is mostly related to devices attached to the rail itself. It wasn’t clear if an aimpoint on the upper receiver would be drastically have POI shift from this, versus a laser on the rail.

    So maybe I put MK16 on a few uppers with no lasers and then some more heavy duty rail for the one upper with a laser (for night vision work)?

  2. #2
    One more thing, these threads I perused suggested a rail that had an opening over the gas block would be better since If the rail bent, it wouldn’t touch the gas block. I only recall seeing a single rail do that in my previous research, a noveske, designed to give access to their adjustable gas block.

    But I’m wondering now, as maybe silly as it sounds, to take an MK16 and carefully cut an opening where the gas block is. I don’t need a full rail anyway on top of accessories. Maybe even cover it with a rubber rail cover that would be flexible and move if the rail bent and otherwise would push the gas block against the rail cover.

  3. #3
    Mk4/8 are regarded as the better rails for lasers, and that’s what I run. I have three of them. The KAC URX rails are regarded as super sturdy for laser use too, and of course one is installed on my SR15

    That’s being said, it’s pretty hard to bend a rail, and of course, the longer the rail, the more leverage to bend it.

  4. #4
    Member Wake27's Avatar
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    This was a huge deal, at least in the sense of how emotional people got over it. Seen lots of shit back and forth about it without more than some sketchy "proof" and testing. I think its very plausible that any light weight narrow tube of a rail may contact a gas block but in this argument, people seem to forget that the barrel flexes too. So pair a light and narrow MCMR/MK16/whatever with a barrel that is supposed to flex, a gas block that is unnecessarily large as it is in many cases (I love BCM but their .625 gb has the same OD as their .750 gb I'm pretty sure, G's old ones were apparently large as well), and a huge cantilevered weight (the ARFCOM thing came from a MAWL which may be cool but is a giant thing hanging off of one side) and yeah, chances are good that some shit will contact.

    Whether all of that results in a dramatic POI shift for your setup may be entirely dependent on the sum of all factors, especially considering the wide variances you can have in an impact. But at the end of the day, do you expect your gun to take that hard of a hit, and at the same exact time, your only option is a laser or front sight in a two way shooting incident? When I get into NODs and lasers, they'll likely go on my URX4s but I'm very happy with my MCMRs and MK16s and want more of both. I do pair them with small gas blocks when possible but the only real justification I can see for significant concern is MIL usage and even then, there needs to be more data before anyone does anything. There was a big concern over the M855A1 round cracking uppers that was complete bullshit and came about this exact same way.

  5. #5
    I heard some of this stuff when it was going around too but Army SF has been issuing the URG-I uppers with Mk16 rail for a while now. Have there been reports of these issues from field use or just these third hand reports from some initial testing?
    My posts only represent my personal opinion and do not necessarily reflect the opinions or official policies of any employer, past or present. Obvious spelling errors are likely the result of an iPhone keyboard.

  6. #6
    Not only are SF issuing the Mk16 upper, the 75th Ranger Regiment is also issuing them as well now. I'm going with another case of internet rumor blown out of proportion. I followed it all fairly closely at the time and there was a lot of speculation and people pretending to have inside knowledge about contracts being cancelled, etc. that never came to be.

  7. #7
    Don't use a giant low profile gas block, and you'll be much less likely to impact the sides of the handguard (it's not a rail, guys); they were using MK12 gas blocks during the tests, IIRC, which barely fit under. Deflection is not just an issue of the rigidity of the handguard itself, but also how it interfaces with the barrel nut, how long the overall handguard itself is, etc., so a cheese grater isn't going to necessarily help much, despite all the extra material. I've also been told that a big issue was that there was relatively loose fit between the barrel nut and the handguard itself on the MK16s (at least for that batch back then), and when combined with the relatively soft aluminum barrel nut, impacts would permanently deform the barrel nut and cause shift; the fact that the legendary MK1s were made with 7075 barrel nuts, and so are the MK4s and MK8s, makes me think that 7075 barrel nuts are fine, as long as tolerances are properly held.

    If you're so worried about all this shit, just get a monolithic upper and call it a day.

  8. #8
    In the ar15.com thread that got deleted, there was no evidence of any damage to a barrel nut. There was visible damage to the 12 o'clock rail on the handguard where the MAWL was mounted that would have accounted for the reported zero shift. I have never seen any proof that the barrel nut was somehow related to the 1 reported URGI incident. Based on the photo it seemed fairly obvious to me that the inside profile of handguard under the 12 o'clock rail has a stress riser and that the damage was due to the combination of that and the way the MAWL is attached. There were many rumors flying around about replacing the aluminum barrel nut with a steel one, which to my knowledge has not been substantiated.

    I would also be hesitant to trust hearsay even from people who claim to have inside knowledge. At the time I talked to a lot of people who acted like they had inside knowledge about the URGI and in the end all their information was obviously publicly available in that one leaked powerpoint slide and the ar15.com thread. But none of them would outright come clean and say they were just going off stuff they saw on the internet.

    Among other fun (unsubstantiated but often repeated) URGI rumors:
    The real reason there was zero shift is because the offset placement of the bolts clamping the rail to the barrel nut results in less clamping force
    The gas block is whipping around inside so hard it can destroy the rail from the inside (???)
    Last edited by Eyesquared; 05-09-2021 at 04:49 PM.

  9. #9
    I do have a MAWL that I picked up recently, so I am concerned about this issue. I am planning to put together some new upper to use it with, so for now, it’s in the box.

    I’m a bit concerned about the 13.5” Mk16 I picked up recently, intending to use with a 14.5” new barrel that has mid length gas tube. Because from my reading, speculation existed that mid length are more prone to this potential issue since the gas block is further from the receiver and thus a slight angled bent to the rail would contact a mid length gas block before it would a carbine one, based on trigonometry.

    I do like this 13.5” MK16 and I’m not planning to put an IR laser on all of my uppers, just one of them. So maybe I use this MK16 for a different build, and I buy something like the Larue quad rail (4-way pic rail) to use with an upper for the MAWL? It will be a bit heavier but the MAWL gun is my zombie LARPing gun, not a “carry gently from the padded case to the firing line” gun.

    I don’t love the MAWL but it seems like the best civilian IR laser on the market now. So I’m kind of stuck with the hand off the side thing until a better civie laser comes out.

    I like lightweight pencil barrels in general so even if the rail is heavier, perhaps the weight will be offset by the lighter barrel. I do plan to run it with a mini 556 silencer, too, if that matters.

  10. #10
    Quote Originally Posted by Sanch View Post
    I do have a MAWL that I picked up recently, so I am concerned about this issue. I am planning to put together some new upper to use it with, so for now, it’s in the box.

    I’m a bit concerned about the 13.5” Mk16 I picked up recently, intending to use with a 14.5” new barrel that has mid length gas tube. Because from my reading, speculation existed that mid length are more prone to this potential issue since the gas block is further from the receiver and thus a slight angled bent to the rail would contact a mid length gas block before it would a carbine one, based on trigonometry.

    I do like this 13.5” MK16 and I’m not planning to put an IR laser on all of my uppers, just one of them. So maybe I use this MK16 for a different build, and I buy something like the Larue quad rail (4-way pic rail) to use with an upper for the MAWL? It will be a bit heavier but the MAWL gun is my zombie LARPing gun, not a “carry gently from the padded case to the firing line” gun.

    I don’t love the MAWL but it seems like the best civilian IR laser on the market now. So I’m kind of stuck with the hand off the side thing until a better civie laser comes out.

    I like lightweight pencil barrels in general so even if the rail is heavier, perhaps the weight will be offset by the lighter barrel. I do plan to run it with a mini 556 silencer, too, if that matters.
    I don't think the midlength or carbine gas is pertinent at all. I think the theory that the gas block is whipping around inside the rail and then destroying it from the inside is silly, and without even doing any math, it strains credulity given a basic understanding of vibrations. The barrel of an AR is stiff enough that even if it vibrates a bit when the gun is dropped, I am very skeptical that the gas block will get enough energy going to damage anything meaningfully. The issued configuration has midlength gas, too.

    I would put the MAWL on the gun and try not to smash it into things but I would not be overly concerned. From looking at a friend's newer Mk16 it appears that Geissele has revised the extrusion die so that the corners under the 12 o'clock rail have a larger radius hence less of a stress riser. Either way, with the old or newer rails, the interior profile there is still as strong as many competitors' rails like the BCM, KAC, or even the DD RIS2. The cross section is also as strong as the Mk4/Mk8 that many people claim is good to go. The Larue rails are pretty overbuilt in this area if this is really a dealbreaker, but I'd just run it as is and if it breaks, make Geissele make it right.

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    Last edited by Eyesquared; 05-09-2021 at 06:06 PM.

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