A few thoughts on the M16A4.


The FN M16A4 I carried in Iraq.

When I enlisted in the USMC I was issued a M16A2. Other then when we occasionally added a PEQ-2 IR laser, a flashlight, or the issued M203 grenade launcher, we felt this gun did everything we needed it to do.

We didn’t know about things like quad rails and quick detach accessories. Those introduced a whole different mentality to how to use our weapons.

When the M16/M16A1 become the M16A2 it gained about a pound. From the M16A2 to the M16A4 it gained about another pound. Most of this comes from the Knights Armament Corp. (KAC) M5 RAS rail system. The KAC M5 RAS is a good rail system, but it has been surpassed by much lighter better free float rails.

That additional weight, combined with the weight of various lights, lasers, and optics along with the fixed stock not playing well with our body armor made using the M16A4 a great deal more awkward. There was a huge difference between just wearing ALICE gear and shooting a M16A2 verses wearing an Interceptor vest with plates and MOLLE II gear shooting a M16A4 with ACOG, PEQ-2, and a Surefire.

My Colt AR15A4 with Trijicon TA31RCO-A4

Since I got out of the military, I have owned several rifles similar to the M16A4. I had a Bushmaster, a BCM, Saber, and now a Colt AR15A4. Most of these guns I shot for a while then got rid of. The reason for that is that the M16A4 is not particularly special at anything.

I have often told people that the M4 is a jack of all trade, but master of none. Truthfully, the M4 really excels at many of the roles it is used in. The M16A4 type rifle falls into an odd place where it doesn’t particularly do any one thing significantly better than the M4, yet is inferior in handling and weight.

The M16A4 is not a precision rifle. While it is more than accurate enough for combat, it is not a sniper rifle. If your planning to shoot in Rifle Competition, you would be better off with a rifle with a fixed carry handle with match sights, and a free floating match barrel.

While the M16A4 isn’t overly large or heavy, it certainly is not as handy for shooting indoors or confined spaces. The M4 and smaller guns show distinct superiority in handling while in close quarters shooting conditions.

While I was in the Corps we were generally of the belief that the M16A2/A4 was a superior weapon system to the M4. Statements of increased accuracy, reliability, and lethality (due to increased muzzle velocity) were occasionally thrown around.

When using Iron sights, the longer sight radius of the M16 is clearly apparent over the carbine. However most of us no longer use iron sights as our primary way to aim, so this is a moot point. As for mechanical accuracy, the M4 doesn’t give anything up to the M16.

Around 2005-2008 or so I often recall reading on the major gun forums that the AR15 rifle is so very much more reliable than the Carbine. We do know that the rifle has lower gas port pressure and should be easier on components than the carbine. Still for most users they will not see a reliability benefit from the rifle. Not to mention the carbine is clearly reliable enough for groups like the SEALs, U.S. Army, and various foreign special forces groups. So back in 2006, the M4 was good enough for the US SEALs, but not a good enough weapon for the USMC infantry.

While I was in there was a push to give the Marine Infantry M4 carbines. This was considered foolish. Later after I was out there was a push to make a “Product Improved” M16A4 with features like a free floating rail, and a compressible stock. I have heard that from several sources that the USMC decided instead to just give infantry Marines M4 carbines. In 2007, shortly before I got out, one of the other unit got brand new M4 carbines. When I inquired why, I was told that one of John McCain’s son was in that unit. I don’t know if that is true, but it sure seems like the type of reason one unit would get superior equipment. Clearly the M4 is good enough for the USMC now.

I like the M16A4 configuration, but I own one more for plinking and nostalgia. I firmly believe that the majority of AR15 user would be better off with a good carbine than the M16A4 configuration.


  1. Concur. This year I built an A4 clone (mostly BCM); I was very pleased with the build until I spent some time carrying it around my property, getting in and out of vehicles, and shooting at ranges generally under 200 yards. I came to a pretty similar conclusion, namely that I wasn’t gaining anything over my 16″ carbines while adding weight and clumsiness. The A4 clone got sold.

  2. Good reasoning. The debate continues about the effectiveness (or lack of) of the short guns to perform as well due to the loss of velocity. The M4 fills most needs of the troops. That is why members of a squad carry specialty weapons. Like a true snipers rifle, and belt fed machineguns.
    I started out with M16A1 rifles, and like that weapon. It is a good weight, only the length detracts from its usefulness. If cleaned properly they work and work well.
    The A3 (A4) is heavy. The fixed stock doesn’t adapt well to body size nor armor thickness. The M4 adjustable stock is a great improvement. What are the real facts about rifle effectiveness? From all I see the M4 performs well. Barracks talk, is often very unreliable. If the M4 is as bad as some claim, it would be replaced in the spec ops arena at a minimum.

  3. The A2 did not add a pound over the A1.
    The M5 RAS did not add a pound either, unless you ignorantly left all the rail panels on, especially the ones on the top rail.
    The only way you come up with such weights is if you don’t subtract out what was replaced.

    • Hello Mr. Lutz,

      A couple of points.
      First I said “about” a pound.
      Second, KAC lists their M5 RAS at 17 oz. http://www.knightarmco.com/portfolio/m5-rifle-ras/ Even with out the panels, that still is “about” a pound.
      Lastly, I don’t have issued rifles right next to me to measure, but I do have a copy of FM 3-22.9 handy. The US Army says the M16A1 is 6.35 pounds. The A2 7.78 (1.43 pounds heavier than the A1). They also list the M16A4 at 9.08 lbs. (1.3 lbs heavier than the A2).

      Now I don’t expect the numbers in an Army publication to be correct. But this pub claims that each rifle is over a pound difference in weight.

      Do you have more correct information?

      • I stand partially corrected.
        The different TM’s and FM’s are all over the place with weights, and then I am not sure the buttstocks are, or are not loaded with cleaning gear.
        My collection of manuals show the following:
        1991 dated TM…23&P for M16A1 with Sling & loaded 30-round magazine: 7.96 lbs.
        Unloaded and no sling: 6.55 lbs.

        April 1977 dated M16A1 TM…10 Operator’s Manual: loaded with 30 rounds: 7.9 lbs.

        Oct 1998 dated M16A2 TM…10 Operator’s: loaded with 30 rounds & sling: 8.79 lbs.
        So I was wrong, because 7.9 subtracted from 8.79 is .89 lbs., which is fairly “about a pound.”

        The TM…23&P dated Nov 2008 for the M16A2 and A4 loaded with 30 rounds are as follows:
        M16A2: 8.81 lbs.
        M16A4: 9.13 lbs. (However, the A4 illustrations show a BUIS mounted to the upper, and do not show any panels installed on the M5 RAS forend.)

        I just remember in 1983 when we briefed the Commandant of the Marine Corps on the M16A2 acquisition decision, the weight difference was a few ounces, and nothing near .89 lbs. In fact we illustrated the weight difference with a small can of cheese spread and a similar tin of peanut butter from the then current C-Rations for the officers there assembled. That pretty much de-bunked the ‘weight increase’ issue. I also remember there was only one Marine in the Operational Test Squad, that when blindfolded, could tell one M16A1 test rifle from one M16A1E1 test rifle.

        The bottom line is that the M4 Carbine is lighter in weight, but that surplus is seemingly always taken up by adding some other piece of “lightweight” equipment. I mean in Viet-Nam, we ended up humping the same weight of gear and ammo with the M16 as we had with the M14.

  4. I stand corrected a second time. As I have thought more about the C-Ration can comparison we made to the ‘weight increase,’ it was only the weight added to the barrel we were referencing in the brief. Senior leadership at the decision brief had no issue with the minor weight increases with the adjustable rear sight, lower receiver strengthening and buttstock length increase (5/8″), but the “heavier barrel” was an issue with them because its title said “heavier.”
    Sorry for the clouded memory, but its kind of amazing how the old disk drive (68 years old now) is able to cycle your old memories around and bring them to the forefront.

    • Don’t get me wrong, I am not saying that the increased in performance of the A1->A2->A4 are not worth the increase in weight. I just believe for the layman and for infantryman, any benefits of the M16A4 are not worth it over the M4.

      As we change gear, we change some of our nuances in how we use that gear. For example: The A2 stock is a very durable and well made stock. In SOI EAST we would use M16A2s as hasty lifts, with one Marine holding the stock and another the barrel to hoist a third Marine student up a wall. I’ve hit more than a few people with the A2 stock. It makes for a decent club. One of the arguments against the M4 I used to hear was how much weaker a collapsible stock is. Some of the things our troops have learned to do is not use their guns as ladders, and to strike with the muzzle instead of the stock.

      There is no perfect gun, we need to pick what best suits the type of shooting we will be doing. I wouldn’t suggest the M4 for the High Power competitor. Nor would I suggest it for the persons whose sole goal is to shoot sub-MOA groups at extended ranges. But for the person who may have to shoot another human in realistic combat distances, I have a hard time suggesting something other then the AR15 carbine.

    • As a more recent Marine combat veteran, who used the M16A4 in Iraq, and the M4 in Afghanistan, I can say with some certainty that the longer rifle is indeed significantly more reliable. Both benefit greatly from keeping them lubricated at all times, but the ONLY broken bolts I ever saw or experienced were in M4’s. Recoil, though only modest to begin with when compared to larger battle rifle calibers, was more manageable in the longer guns as well. I personally resented the long, fixed stock, which did not pay well with our bulkier modern armor systems.

      Now that I am out, and compete in civilian gun games, I think military (and Corps specifically) would have done better by going with a free floated, 16″ barrel with a slightly heavier than “government” profile behind the gas block, and a midlength or Intermediate length gas system. On the back end, an A5 buffer tube and buffer system with a collapsible buttstock (take your pick) would have given us the heavier weight and longer spring travel of the rifle buffer system, but the compact and user adjustable benefits of the M4. The H&K M27 IAR that we now use is more accurate than either of the legacy M4 or M16’s, primarily because it is free floated. But it suffers bolt life issues beyond even what plagued the M4, because of excessive bolt thrust (the system was designed for a 10.5″ barrel, not a 16″ one). I can put together a very accurate (1.5 MOA or better with bulk 62gr, 3/4 MOA with handloads) free floated midlength 16″ carbine that is lighter and smoother shooting than an M16, but far more reliable and accurate than an M4, for about $800. I’m sure the government could do much, much better than that.

  5. What “off the shelf” components would you recommend towards building an improved “M16A5” variant? Could you build one and post it up on this blog?

    • There are two main changes in most “improved” M16A4 concepts. The first is a colapsible stock, and the second is a different rail system.

      The Canadians have been running collapsible stocks on rifle uppers for a long time now. Two other systems have been made for converting the rifle to have a carbine stock. One is the VLTOR A5 receiver extension, the other is the H6 buffer. Either of these are suppose to grant improved reliability over just using a car buffered collapsible stock on an A2/A4 upper.

      The KAC M5 RAS is a good rail system. But at a MSRP of about $323 (last I checked) there are cheaper, better, lighter freefloat rails now. If you wanted to retain the ability to mount a M203, the Daniel Defense M4 RIS II rail would free float the barrel, and allow for a M203 to be mounted. The KAC URX is similar, but I believe they have dropped the ability to mount a M203.

      If you didn’t require the ability to mount a M203, there are a number of free float rail systems that are cheaper than the MSRP of the KAC M4 RAS. I used to recommend the Daniel Defense M4 Rail, but it appears to have been discontinued.

      The H6 buffer would have an advantage for the military as they could use the same carbine stock parts for the rifle and carbine except for the different buffers.
      I also like the idea of the military using something like the DD M4 RIS II rail. They could use the same rail on the carbines and the rifles. Helps keep things simpler for procurement and the armorers. I believe the earlier KAC URX also had a similar concept in mind.

      After those main changes, there are countless other things you could change, but those are less important.
      Some would suggest a different profile barrel. The A2 profile is heavy near the muzzle, since the barrel would now be free floated, a different profile could be used. However adopting a new barrel may not be practical across the military.

      For a privately owned firearm, some might consider a match barrel for an increase in precision. Many wouldn’t need this as many don’t shoot well enough, or don’t require that capability. The standard A2 barrel is rather accurate, but it is not a precision rifle. Switching to a match barrel is probably not the best choice for an infantrymans rifle.

      In the past, people have chopped A2 barrels for better handling. Some would even chop the barrel to right in front of the gas block. This became known as a “dissapator”. Unfortunately many of these “dissy” rifles had functioning issues. Other than the rifle length iron sights, you would have been better off going to the carbine.

      It seems to me that most of the ~improved~ M16 concepts are simply trying to make a stop gap M4. Perhaps it would be better to look at the carbine and see how to improve that. In times past I have seen arguments for a 16 inch barrel on a military carbine. We have various military groups using the C8SFW with a 15.8 inch barrel(I’ve seen it reported from 15.7 to 15.9, I don’t have one to measure so please don’t anyone nit pick) and the M27 IAR with a 16.5 inch barrel.

      I really felt that with the IAR that the Corps wanted a M4, but they weren’t going to buy the M4, so they tried to find something similar enough, yet different enough.

      So in the end, my improved A4 would probably end up something like this:

      • If you want to try and clone an M16A5 PIP clone, start with a MagPul UBR, or a Vltor A5 stock, add a M4A1 12 inch RIS II DD rail, and and go 16 inch or keep the 20 inch barrel, however you must utilizes a low profile gas block. Obtain a pair of KAC flip ups (0-600 rear and Mk12 front). Those components make up the A5 PIP as their were several variations being tested.

      • Thanks for the info. It’d be interesting if you could construct that model and try it out on the range for comfort and the like.

        Going on a slight tangent, how well would a 40mm Grenade Launcher with a longer barrel that extended to the length of the muzzle of an M16A4 do? Doesn’t the older M79 have a longer effective range than the newer M203 and M320 due to its longer barrel compared to those two models?

      • The Dissapators I have seen had carbine length gas systems (cut down under the handguard) with an A2 sight tower at rifle’s length on the barrel. Essentially they were carbines with and extended sight radius. Not unlike what you can do with a micro gas block and 15″ free-float rail and a rail-mounted front sight.
        I have seen some “chop jobs” and yes, they DID have functioning issues.

  6. When I was an active duty Marine, my rifle was the standard 20 inch rifle. I am of the belief that the lower reciever should be the only part thats standard issue. The rest of the rifle should be mission specific.
    In my retirement years, My shooting needs are best met by a 20 inch rifle.

  7. It’s nice that you made an example of an “M16A5” in a later entry, but I’m surprised you closed down the comments to entries newer than this one, given that the comments here were perfectly civil. I’d certainly like to ask a few questions about your proposed build.

    • Comments were closed because for each civil comment we had multiple not so civil comments that we would not allow to be published. Not to mention the ridiculous amounts of spam. Having to delete countless personal insults finally pushed us to close commenting on new posts.

      • Damn, it’s a pity that this blog can no longer engender good discussion directly on it. Is it possible to implement a captcha system to keep out spammers, at least?

        Anyway, it seems that there are upgrades in the pipeline for the M16A4’s main users, the USMC. You can read about it here:


        A short list of improvements include new optics, a free-floating barrel, compensator, and a new trigger. It could be something worth looking into.

        And why did the author of the “Re-thinking the Modern Rifle” article here say it was a bonus that s/he didn’t have to mention bayonets? Would they not have worked well on the 18-inch barrel length? And just how much easier is a difference of 2 inches when it comes to handling, between a 20-inch or 18-inch barrel?

  8. First the he’ll with the m4. it’s for clowns who can’t shoot in the first place as a marine infantry man of the 1st bn 5th Mar c co wpns plt and alpha comapany 1st recon battalion I would use a m16a4 over any weak ass m4 any day now matter who built it. I used in the first fallujah. I used it in ramidi. Iraq I used in South Sudan I used in the southern Phillipines. I used in mount and cold weather, swamp, and jungle terrain. It proved itself to me in multiple combat missions. It saved my life. and yes I used iron sights before any other optical sight. If you can’t shoot with iron sights than you can can’t aim and shoot in the first place. I served from 2001 to 2009. M4 are for the army plus you can’t use the kabar bayonet with a small barrel m4. We used the fallujahand all around the akbar Providence. And I used the m16a4 in many mount missions just fine. Those who wine and complain about the use of weak ass m4s need to spend more time in the line units and the m16a4 will out perform any m4 any time. It proved it worthiness to many infantrymen over any m4 in many firefights.

    • Your better call up your leadership and cry to them as the USMC is switching to the M4.

      Your poorly worded, factually incorrect argument is the type of dribble that makes all Marines look stupid.

  9. they should switch to the ruger mini-14- change out wood stock for a collapsible para trooper stock like the a- team had—– all i know is the M-16 and teh M-4 were a piece of crap when dropping out of CH-53 under sandy conditions– many times it was hard to pull teh charging handle and get everything to flow again– ak -47 would still fire and so does a mini-14 when all sanded out

  10. Late to the party, but here goes….. I never served in any branch of the military, and I’m an old man now. I’ve built and/or purchased a number of AR-based guns over about 15 years now – starting with a 24” heavy barreled varminter, several carbines (still own two), a 10.5” SBR, an 18” SPR, ………..and…….a replica of an M16A4 I just completed yesterday. I haven’t even shot it yet. I went with the gov’t profile 20” barrel, and there is no doubt that the KAC M5 RAS is heavier than other rail systems I have on other ARs, but it was important to me for purely esthetic reasons to have a reasonably close facsimile of the real deal, and inasmuch as I’m a gimpy old fart with a limp and a bad back, I’m driving to the range, not humping it, so I don’t care about the weight that much.

    I suspect you’re right about accuracy…….in fact my SPR is VERY accurate, so it is unlikely that the A4 will get close to that; but I don’t imagine that the A4 would be any more accurate than one of the carbines or my SBR either.

    But that doesn’t matter to me, because I didn’t build the A4 because I thought it was a superior gun to the other models. I built it because I wanted to pay tribute to the genre. Despite its extra weight, I like the heft of it. It seems well balanced. For now, it’s wearing an ACOG, but when I get my cataracts removed in a few months, I’ll put the carry handle on it and probably leave it that way.

    In a sense, it reminds me of another rifle I own – a Ruger Gunsite Scout – because even though it does no one thing exceedingly well, it will do most things well enough. The Ruger isn’t anywhere near as accurate as my Remington precision rifle, but it is 10” shorter and weighs about 5 lbs less, and it is “accurate enough” for what I call “practical accuracy”. As such, the Ruger is a good “general purpose rifle. And just as the Ruger is a pretty decent “general purpose” rifle in the .308 bolt gun class, I think the A4 will kind of fall into that category……just a decent general purpose rifle in the small bore class, and there’s always room in the safe for something like that.

  11. Geeez……..some of you folks get downright cranky here…..I have a Stag Arms free floated 18″ that I stuck a Timney trigger on and at 100 yards can make cute cloverleaf designs on paper and with my metal flip ups I can generally maintain a 2″ group depending on how much coffee I have on board.
    I will defer to the vets making comments here out of sheer respect but my son gets some very good results with a 20″ “retro” Stag he bought. Heck, he even paid about as much for his optic as he did for his rifle but at least the removable carry handle let him learn the basics of how to properly use iron sights. His isnt free floated and doesnt group quite as well as mine but for its true purpose it is more than accurate enough. I ditched a Colt 6920 I had simply because the little carbine couldnt shoot as well as I thought it should……..not a huge fan of the 16″ or the carbine length gas system. Even my intermediate length system allows me to get back on target a lot faster than I ever could with the carbine length…….and I do concur with free floating improving groups by at least .5″…..
    Interesting threads. Proud to even post along with people I am so proud and thankful for.


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