Where are they now? Monolithic Uppers



I was looking at a picture of the LMT MARS-L as adopted by New Zealand and I was remembering how not that long ago I read all sorts of people saying that the future of the AR was going to be monolithic uppers.

Greater rigidity, accuracy & precision, no top rail gap interfering with optics mounting, simpler and less parts, and all manner of other improvements were the reasons why the monolithic upper was the future.

I tended to point out that if the handguard got damaged, then you had to replace a whole larger more expensive assembly.  Don’t get me wrong, I like monolithic uppers and I own a few.

For example this Colt LE6945 pictured has a monolithic upper.

So what was it we were suppose to have by now?

There was going to be this M16A4 Product Improved(Sometimes referred to as M16A5).  This was going to be the USMC new rifle which would be a collapsing stock(Some sources said VLTOR A5, others Magpul UBR) and a VLTOR monolithic upper.  It might have looked something like this:

Photo found on AR15.com

The USMC ended up moving to the M4 and the M27 IAR.  We don’t know how seriously the Corps ever really considered the Product Improved M16A4.  But that didn’t stop rampant speculation by gun nuts.

Anyways I think that the ultimate customization available to the AR is what killed interest in the monolithic upper.  For example some years back Noveske barrels were extremely popular on high dollar custom AR15s.  The more popular monolithic uppers like the LMT MRP used proprietary barrels and so people couldn’t use what ever is the flavor the week.  Similarly preferences in handguards changed.  We went from people wanted a M4 barrel with KAC RAS, to a long free float quad rail, to long slick tubes.  Now MLOK and Keymod are everywhere(but it looks like MLOK is winning).  Someone who bought an expensive monolithic upper is locked into their choice.

I think the monolithic upper has lost out in the AR market, but I expect most any new competitor to the AR15 will likely have a monolithic upper with perhaps something like a removable or interchangeable side/bottom section.


  1. I say this as an owner of an LMT MWS and an MRP – monolithic uppers are a good concept, but not really necessary for the AR15 platform.

    However, one specific instance where a monolithic upper has an advantage is with a rail mounted laser/illuminator for nvg use. You know with absolute certainty that your laser zero won’t change no matter how hard you grip, twist, or lean on the rifle. The same cannot be said for the majority of free float handguards on the market. Even the much sought after DD RIS II isn’t as rigid as most people think; if you put a vertical grip or barricade stop on it and lean against a wall you can easily watch your co-witnessed irons (if using a red dot) or laser diverge from your aiming point. Most likely this is to blame on the barrel nut arrangement, since it has very little contact surface area due to how it clamps the front/back of the nut. A friend at BE Meyers once told me that Geissele’s handguards exhibited the least amount of shift under stress due to the long barrel nut with plenty of clamping area.

    LMT makes very accurate barrels, even their chrome lined ones typically shoot around 1 moa with match ammo, but I have found they don’t last as long as something like the FN hammer forged barrels. Replacement cost is a fair bit more, too. Also, LMT likes to talk about how you can switch calibers easily, but it’s not like that’s an issue with a non-monolithic upper, either. Pull two pins, swap the whole upper, and assuming you have a separate optic on both, there’s no need to re-zero.

    • I’ve been meaning to post about POI shift in FF rails. I read a claim about 5′ shift at 100m and at first I thought that was silly but when I started to do the math it seems very likely.

      • It depends on how hard you pull on the handguard. Highpower shooters all use a freefloat handguard with the sling attached to said handguard because the extreme sling tension would otherwise pull the barrel (and fixed front sight) off to one side.

        It is very easy to see the shift in real time if you have a rifle set up with a red dot and co-witnessed iron sights, with the front sight mounted to the front of the handguard. You can tension a sling or man-handle a vfg attached to the handguard and watch as the dot diverges from the irons as tension is applied.

        • WILL I have recently been buying some stuff from Arisaka defense and I have to tell you I am really pleased with the things I have gotten. I have a article for the the website planned for later this week about them as a matter of fact. I was a little surprised when I came here to approve comments while on lunch and saw your emails address. I bought the stubby VFG and a M-LOK QD sling mount and I have to say I really like it. very impressed with it.

  2. I’ve had an MRP for several years and it’s a good shooter. It does what it’s supposed to do. LMT makes good kit but no matter how well machined swapping out a barrel means checking zero each time. It’s always close, and depending on your tolerance level maybe “good enough,” but having a separate upper with its sights and/or optic zeroed just makes more sense to me. Given the price it makes financial sense too.

    The continuous top rail however has some value added. I think it was on here recently a discussion about the Mk12 Mod 0 and Mod 1. The Mod 0 used that ARMS rail to bridge upper and handguard into a solid, continuous unit. The Mod 1 didn’t and suffers its optic to be in a serviceable but less than ideal position. I’d counter with the concept of something similar to the Mod 0 by having a rail bridge upper to handguard being a better working solution.

    • I am 100 sold on the colt 6940 series monolithic uppers. they are great, I love them. the colt barrel nut they use with them makes those guns real tack driving lasers. I love them and own several but the monolithic upper is not suitable to general issue to an Army in my opinion I completely agree with the barrel swap stuff. I found that dubious from the start. like you I prefer the idea of swapping an upper via pushing out two pins, and the uppers already having optics on them already zeroed etc

  3. I think you nailed it early on. Locking someone into the monolithic removes the ability to tinker, especially if it also meant a propriety barrel system.

    I’d say there’s also a healthy dose of wondering just how much improvement you’re really getting for the cost. I don’t think the cost/benefit ratio worked out on that one.

    • Glad to see you still come over and visit us. how are things going over there? I was wondering what you thought about my article were I talked about finally completing the 20/20/20 1K challenge.

      • Oh, you know, life’s been a little hellish lately. The last year since leaving the military has been a wild ride career wise. Lots of new things to learn.

        On top of that, my family suffered a tragic loss earlier this year that killed my motivation to write for a while.

        With the 20/20/20 1k, yet another impressive feat that I would have thought couldn’t be done five years ago. I miss living out west where there was space like that. Well done sticking it to Cooper 😉

  4. Mega Machine had a wonderful monolithic years ago …I truly wanted their round smooth sided version. Colt shut them down with their patent . They did come out with a new version that utilized the inside barrel nut and the longer receiver front end so innovation prevailed somewhat .

  5. Colt Canada makes a beautiful monolithic upper, the MRR, I run the 8.5 300blk suppressed and 11.6″ 556 at work and the semi 11.6 at home. They’re very rugged, have had zero stoppages unrelated to mags or high volume can use and allthough a tad heavier than some, are unbeatable in reliability in even the worst conditions, and its still lighter than the UIR. The stock trigger is the best Ive experienced in any issued rifle ever, and this gun works perfect out of the box once optics are mounted but I will say putting a Giessele SSA-E in my home gun made it almost as fast as my work gun but more accurate doing so.

    Only wish the civilian ones came with the barrel tool, and MBUIS for the price, and that Canada allowed for suppressors civvie side.

    I truly believe you could use these as a baseball bat for a day and there would be no change in accuracy.

    Very excited about the monolithic DMR options being made now (Colt Canada C20)

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