Colt Modular Carbine CM901

David Crane got an exclusive on the new Colt Modular Carbine CM901. It is one nifty looking rifle.

Colt’s CM901 is designed as a multi-caliber, modular capability with one lower receiver configurable to different calibers and barrel lengths for different missions. With its universal lower receiver based on the 7.62 mm round and the ergonomics of the M4 and M16, the lower receiver is also compatible with the upper receivers and bolt carrier assemblies of all existing Colt weapons in the military inventory and its newly developed weapons and alternative operating systems from 7.62mm to 5.56mm. Colt has kept its solution simple, operationally and cost effective, and easily adaptable for the warfighter and the support base.

Lots of info, photos and video at DefenseReview.

Steve Johnson

Founder and Dictator-In-Chief of TFB. A passionate gun owner, a shooting enthusiast and totally tacti-uncool. Favorite first date location: any gun range. Steve can be contacted here.


  • Canthros

    Might just be me, but it seems like an opportunity to cram the wrong magazine into the gun. That said, it does seem like something that has some potential on the civvy market in some ban states. Assuming the ban doesn’t get overturned first.

  • Boris

    It’s an AR with an exchangeable magwell. whoop-di-frikkin-doo.

  • Dave

    In one of the images on DefRev, several uppers are shown with part of the picture redacted. However, the reflection on the table just below the redacted area shows a reflection of what appears to be the adapter that allows for the caliber/upper swap. It looks like a mini-magwell pins onto the 5.56 upper’s front receiver pin location and provides a bridge to the new universal lower’s front receiver pin hole. During assembly, the 5.56 mini-magwell would just be inserted down into the 7.62-sized magwell of the lower from the top. Presumably the lower’s mag release will interface with a release on the mini-magwell. Neat design.

  • Pete Sheppard

    “What is wrong with this picture?”
    NOTHING! Provided it’s the Colt CM901, which is supposed to accept 5.56 mags right along with 7.62s.

  • SDanger

    Keep your booger-hook off the bang-switch until you are ready to fire.

    • I was just alluding to that fact that a 5.56mm mag is in a 7.62mm mag well 😉

  • Colt may have pulled their bacon out of the fiscal fire. What’ll sell this rifle is the lack of new training and new tools. Hell, I could clean this with the cleaning kit I was issued in basic.

    And yeah, unless the trigger man was shooting the rifle, he needed to keep fingers out of the trigger guard.

  • snmp

    That sound like a MGI Multicaliber AR lower with magwell adapter for SANTAG mag or AK mag


    Colt CM901 :
    * Multicaliber Lower with magwell adapter (SANTAG, AK, SR25-AR10 ….)
    * magwell adapter
    * Pre build Upper in diffrent calibers : 308, 7,62×39 M43, .223 ……
    * Upper with DI or Piston
    * Bolt & Bolt Carrier in diffrents calibers

    * UPPER
    * Lower diffrent calibers mag (SANTAG, AK, MK17 ….)
    * Barrel : 308, 7,62×39 M43, .223 ……
    * head Bolt in diffrents calibers

  • ap

    What?! They’re talkin’ Digital when it’s clearly Multicam time!

  • I guess that front pin pivoting adapter is their patent for this carbine, “An Adapter to Accommodate AR15 Uppers on AR10 Lowers”. 😀 Sure seems paranoid to me.

  • Canthros

    One other thing that occurs to me is adoption of this or something like it would make transitioning to more powerful cartridge than 5.56NATO a relative breeze, without bringing all of the trade-offs associated with something like an AR-10 along for the ride.

    (I think the likelihood of the US military adopting this is basically zero, mind.)

  • Sian

    Real standout to me is the integration of ambi controls. I just wonder how much the lower weighs compared to standard AR15.

  • Rijoenpial

    Hi guys…

    So, all that COLT has come up with is something that Future Weapons has shown: just change uppers and just use the same mag well! Well, very brilliant concept! Too bad many have thought about it before!

    They will still have to get new complete uppers, sow wher is this gonna make it LESS expensive?

    They could get either the mag wells to attach to their 5.56 or 7.62 uppers, but where is this novelty? The only thing ‘novel’ is the SAME magwell for both calibers! And it looks goofy and ridiculous! It looks like the Lancer Magwell replacement, although that one was for easier 5.56 mag inserts, not multi caliber mags! But it looks as goofy and ugly as that accessory from Lancer!

    The fact is that this is YET another AR!

    I agree with those that state that multicaliber weapons are unnecessary and just adding to the bulkness of the already heavy soldier! Even if they have the entire upper assembled and ready to go, they will still have to carry in their backpack! Ludicrous concept!

    The idea of two weapons is more realistic, since you hardly change from settings that require longer distance shooting to urban door-to-door firefights…

    And if you do happen to get into those environmments during the SAME mission, then I think a compact lighweight PDW, like the P90, would fit the soldier, together with his Assault Rifle…

    For cost saving purposes, I think this is not gonna decrease costs at all, actually increasing them… It is the same deal that HK had with the piston HK416 uppers to replace the DI ones, only far more costly, since we all know COLT is never cheap, even if their guns are!

    Oh, and they’re still DI! In a time when practically all manufacturers are turning to piston, COLT stubbornously remains with the DI! Maybe they just don’t know how to do piston weapons! Someone just ought to teach them! Well, their COLT APC and their older 703 model never got off the ground, so maybe that’s why!


  • Dave

    It looks like DefRev pulled the picture I referred to, but you can find it on other news sites now like:

  • Dave

    Nevermind. It’s back.

  • Jono

    Trigger dicipline?…. Provided he’s not firing

  • vereceleritas

    I agree with Boris. The exchangeable magwell is the only real news here. Everything else is just different Colt uppers, nothing we haven’t seen before.

    “…Colt has essentially taken the military/tactical AR weapons platform taken to its ultimate logical conclusion, the ultimate evolution of the AR platform, if you will…”

    David Crane seems way too enthusiastic about this. Nothing against Colt, but they must have some awesome tasting Kool-Aid in Hartford. The LMT MRP and KAC SR-15E3 were more important evolutions IMHO.

    On another note, that digital camo finish looks cool, is it anodized in that color?

  • Aurelien

    Definitely not soldier-proof, but it looks nice. Hopefully we’ll see it presented on future gun shows, even out here on the old continent.

  • Vak

    This is nice, but honestly, I don’t really see the point. I mean, it just means that you will be able to keep the same stock and pistol grip on a battle rifle and an assault rifle. You would still have to carry the mags for both weapons, as well as the uppers (and all the tactical doodads you bolt on it, don’t lie, I know you do). (also it’s pig ugly)

    Now, the only person who might benefit from it is the armorer, (disclaimer, I have not served in any branch of any military,) but even then the armorer will just be pissed off to know there’s YET another wonder weapon he has to take care of.

    Still, colt engineers deserves some praise for making a 7.62 receiver that is still compatible with pre-existing 5.56 weapons.

  • Lance

    Looks awesome wonder Steve id SOCOM will buy some lowers since they can use M-4A1 upper with them to save money?!

  • Nadnerbus

    I can see the virtue in this. It’s not revolutionary though or anything. I remember LWRC pimping the concept of a CQB upper for the sniper or DMR, and a accurized long range upper for the regular sniper work, just that both were in .308. The universal lower is the main difference here, and even then it’s not a new idea. Though this might be the best offering of it, time will tell.

    I guess in order to go .308 on a lower that also accepts legacy 5.56 uppers, the .308 upper would have to be proprietary Colt, since DPMS, Knights Armament uppers are longer and will not fit on a 5.56 lower. How would a change in caliber affect spring and buffer combinations? Would those also have to be changed to accommodate the different power rounds?

    For the detractors, they state that it will accept all prior mil spec 5.56 uppers, which also include piston uppers. So if piston really is the way of the future, that can be accommodated.

    When you look at what the military is doing right now, with a mix of small arms and calibers, M14s in old config and EBR config. SCAR Mk 17 and M110 sniper systems, along with M4s and M16s, I can see how something like this makes sense as the logical next step as far as streamlining the whole supply chain and whatnot. But that all depends on the military sticking with the Stoner design, and the merits of that are debatable.

    The idea of a soldier (I’m getting tired of the term “operator”) needing to haul two different calibers on the same mission seems suspect to me, but as a pre-mission configurable options, something along the lines of this could be useful.

    The article was full on in the pocket of Cold though, I’d like to see a more unbiased, in depth review.

  • Rijoenpial

    Hi there

    well, selling a universal lower receiver (LR) still requires the change of uppers for caliber conversion, so, Lance, selling them to SOCOM still require COLT selling them the 7.62 uppers! Since SOCOM already has an ‘original’ 7.62 NATO battle rifle in their inventory, buying full 7.62 uppers seems a sheer waste of money, especially when they already have an evolved piston system and then buy more 7.62 uppers, of the DI persuasion, no less!

    And since COLT is a disgrace in terms of piston weapons (just check how high their APC and 703 model flew), SOCOM would have to stick to a DI 7.62 upper!

    I think they would actually save money just bying more SCARS mk17 than bying universal LRs PLUS the 7.62 uppers! That would just mean, they would just be purchasing MORE 7.62 systems anyway, but from a different vendor!

    And given the costs to SOCOM from purchasing from COLT, I think FNH would be a better choice!

    Would I trust a DI 7.62 system from COLT? Hell no!

    So, the universal magwell is moot compared to the fact that the consumer will still have to buy uppers for them!


  • Redchrome

    Looks like some really nifty and creative engineering. Can’t fault the Colt engineers’ intelligence.

    Also, Defense Review seems to say in most every article “this new thingy works really cool but we’re not allowed to tell you how it works because you’re not cool enough, nyah!”. This is highly irritating.

    All that having been said; it’s a massive effort to maintain backwards-compatibility with a weapon system of dubious design. (I’ll not re-iterate the details other than to say that the AR-18 constitutes an existence proof that there is a Better Way). Colt’s Manufacturing lives and dies by the AR15; and I’m pretty sure they have some pretty powerful incentives (consciously and unconsciously) to maintain that platform.

    Still, for better or for worse the AR15 is very popular, and this design will go far, given a chance.

  • Lance

    Sorry Im going to disagree rijoenpal Ths is alot better than athe debunked SAR series the Colt series has the adavantage of common parts with current M-4s and hads stonger reciver and buttstock than the plastic stock of the FN. The quesetions for Steve so ill leave it to him. The Colt features are better in my opinion. Lets leave it at that.

  • Rijoenpial


    I was expecting you would say that, but I was not talking about that…I was talking about people HAVING to buy COLT uppers, of the 7.62 AND/OR 5.56! So, in reality, you will also need to buy COLT uppers for that Universal Receiver (UR)!

    Also, I reiterate the lack of real need to have a weapon firing BOTH calibers! SOCOM does missions, they know in advance which setting they will be in and which type of warfare they will go up against! So, for SOCOM, the tactical need of these URs!

    Also, point 2, they present a logistical problem, with the soldier still having to carry either full uppers or components such as barrels, bolts, etc in their backpack! Given that SOCOM operators benefit from being ‘light’, only carrying the essentials to augment their mobility, it is folly to be carrying all that extra gear!

    Third, these URs are still in prototype stage, which means that FN can already beat them in their own game! According to FNH, their receivers were already in the test stage by SOCOM, MONTHS before the CM901 was even mentioned!

    And the plastic argument you so often present to diss FN is nonsensical, given that the ACR, be it Remy or Bushy, has the same ‘plastic’ you scorn so much…even more so, counting for the Polymer MOE handguard, which the SCAR doesn’t have!

    So, the plasticky side of the SCAR is shared by the even more plasticky ACR people are so fond of, as well…!

    I’ll leave it at that as well! We’re here to discuss the COLT’s response to the FNH common receiver, not another SCAR debate! I am sure Steve agrees!

    By the way, I actually liked the MGI Hydra, convertible to almost every caliber known, except for the 7.62 NATO! I mean, 9mm, 45, 7.62×39, 5.56, 50 Beowulf, etc… That is what I call a true MODULAR weapon! LOL

    And they can easily add more calibers as well, like the 6.8 Special Purpose Cartridge, 6.5 Grendel… So, talk about an almost unknown truly Modular system! We speak only of the more visible brands, but what about the smaller ones?



  • Rijoenpial

    Sorry, guys,

    I mistakenly posted without ending the tactical need of the URs for the SOCOM, and of course, what I was meaning to say was that there is no tactical need for them, quite the opposite, and here enters the logistical side of the problem!

    Also, I should clarify that the buyers of the COLT’s UR will need to also buy COLT uppers, be it M4 or others, to be able to use these URs! So, any 7.62 uppers you have that are not COLT, won’t be compatible! Hence, why I said that people will need to buy FULL COLT 7.62 or 5.56 or other COLT uppers to make this UR work! It is COLT exclusive for COLT products!

    IT says so in Crane’s Defense Review Presentation: “While the CM901 7.62mm upper receiver is a monolithic upper/rail format with a direct gas impingement (DGI) operating system, the CM901 can utilize just about any 5.56mm rifle/carbine/SBR operating system that Colt manufactures, including the Colt M4/M4A1 DGI system, Colt APC (Advanced Piston Carbine)articulating-link gas piston/op-rod (operating rod) system, Colt AHC (Advanced Hybrid Carbine) DGI/piston-driven hybrid system, and Colt ACC-M (Advanced Colt Carbine-Monolithic) monolithic DGI upper.”

    and here: “Designed to accept all legacy M4/M16 Colt upper receiver assemblies”…

    So, only COLT products, uppers,etc, can work with this UR!

    So this is clearly for Military eyes only, because for a civilian who doesn’t have a COLT AR-15 M4, these URs will be useless!

    I always wondered, how many civilians have COLT M4s at home? Most people have one AR from one of the dozen or more brands out there in the States that produce AR-15s!

    The answer to that question will be indicative of the possibility (or not) of this UR ever reaching civilians!

    So, for the Military, though this may present at first glance, more choices, it will also present a lot more money to be spent on both the URs and the COLT-exclusive 7.62 uppers that these URs require!

    So, in a word, the military will definitely need to buy FULL COLT CM901 7.62 systems, and only then remove the 7.62 uppers and attach their 5.56 uppers to them! Great plan! So, in a word, COLT wants to share the 7.62 NATO inventory with FNH, probably aiming at replacing it!

    I have to say, I hope that given that this is still in the prototype stage, they can make a magwell that doesn’t look as ridiculous as that prototype one!

    Maybe they can make a removable magwell like MGI does that falls in to the weapon system design without looking bulky and ergo very unergonomic-like!



  • Colt can make a piston gun. This way they stay in the game.

    Here is the crux of the problem:

    1) the SCAR needs a torx wrench to take it appart, guess what your typical GI will LOSE the first month they get it?

    2) The SCAR, ACR and other rifles require the army to toss out DECADES of PMI, BMR and other battle drills.

    3) Colt could just make batched of lower receivers for the marines and the rest of the army. Us in ADA land get folding stock goodness and we can re-cycle our M-16 uppers.

  • charles222

    I can see this and using LMT’s MRP upper together as being remarkably flexible. Then you’d have the option of swapping barrel lengths AND some calibers (6.8/5.56 for example) without messing around with totally different uppers.

    My only question is how you’re matching a 5.56mm upper’s receiver pins with a 7.62mm-sized lower; they’re not going to be lining up for obvious reasons. Color me curious. :p

  • charles222

    Edit: lance do you just hate the SCAR or something? The current M4 stock is junk compared to the SCAR’s. The SCAR buttstock is perfectly sturdy and I can factually state it to be so, as I’ve actually shot one.

  • William C.

    Very interesting. It seems there have been several developments from Colt recently. Has anybody heard about more about the Advanced Hybrid Carbine (AHC) or Advanced Piston Carbine (APC)? The former particularly interests me but I haven’t been able to find much about it besides for some limited information from DefenseReview.

  • Redchrome


    1) The SCAR needing a Torx wrench is superior to the AR15 needing a funky special wrench to take the barrel off. It’s not the sort of thing that the individual soldier should be expected to do.

    OTOH If we’re going to debate the business of individual soldiers swapping calibers on their rifles from 5.56 to 7.62 before [or even during] the course of a mission, then yes, the Colt solution is superior to the SCAR or ACR because swappable uppers beats swappable lowers+swappable barrels for ease of caliber convertibility. (Or consider the Tactilite uppers for AR15s that make them single-shot or magazine-fed .50BMG rifles.)

    2) If current procedures follow from a bad idea, then don’t follow the sunk-cost fallacy of “We’ve invested all this time and effort into this thing; let’s not throw it away.” That sort of logic kept us from getting the AR-18, which was cheaper and more reliable than the AR15 in the Army’s own tests in the late 60’s, because the Army had already invested several million dollars into rights and tooling for the AR15. So just because soldiers will have to learn new drills, and some new manuals will have to be printed, does not automatically mean it’s a bad idea. People are capable of rising to expectations and are not just mindless automatons — they are capable of learning new things.

    • 30-06 vs 276

      And also why we had 30-06 instead of .276 pedersen in WWII

  • charles222

    Meh, Defense Review would give a glowing review if somebody put rails and a plastic stock on the .30-40 Kraig. :p

    I tend to think Colt (along with various other manufacturers, such as Noveske and LMT) are DGI believers; (along with 90 or so militaries over the last 40 years.) the APC, IMO, is their “meh, whatever, we’ll pretend this is better” market entry.

    • noob

      Somebody should do a parody defence review article about “the rifle chambered in .30-40 krag (aka .30 U.S., .30 Army, or .30 Government) being fitted to a polymer (aka composite, aka glass reinforced polymer) stock with tactical rails (aka Picatinny rail or MIL-STD-1913 rail or STANAG 2324 rail or accessory rails)” and how awesome it is.

  • Cymond

    I think Dave is right about how the 5.56 uppers attach to the 7.62 lower. It uses a bolt-on block to give the 5.56 upper the same mounting shape as the 7.62 upper. This adapter also functions as a magwell block (like the blocks used to convert a 5.56 to 9mm). So 5.56 upper attaches to block, block attaches to lower.

    I think the logic is that 2 uppers + 1 lower is cheaper than 2 uppers +2 lowers. Of course, its really 1 upper + 1 lower because the military already has a ton of 5.56 uppers. Also, it simplifies the procurement process after the lowers are purchased. Instead of buying new weapons, units can just buy ‘upgrades’. For example, look at the upgraded M24; it is mostly a new weapon but without the procurement headaches of a completely new weapon. Also, the Marines couldn’t procure 1911s (guns), so the bought a bunch of frames, slides, barrels, and other parts. Parts are easier to procure than a completed weapon.

    I don’t think anyone is suggesting that soldiers will go into battle carrying multiple uppers, but rather they will equip themselves for the mission before leaving the basecamp.

    This system is not Colt exclusive! Yes, it only works with Colt 7.62 uppers, but it will work with any milspec 5.56 uppers! Yes, it says Colt! But all Colt are milspec! I love dogs. If someone says “Cymond loves beagles” that is a true statement! But it doesn’t mean I love only beagles! And remember, the AR-10 style rifles are not standardized to the same level as the AR-15! I think Armalite and DPMS are not compatible with each other! The magazines aren’t even 100% cross compatible across all AR-10 style rifles!

    I eventually want a 7.62 AR. Assuming prices are comparable, I’d rather have a 7.62 that can also use 5.56 uppers than a 7.62-only rifle.

  • Lance

    Anyway that is off subject I do think a combo of this with mag pul accessories and stocks will make a awsome carbine.

  • Stella

    I don’t understand the perception that M80 ball is the panacea to the small arms woes of the United States military: its terminal ballistics are not particularly impressive, it’s heavy, loud as hell out of any barrel shorter than 18 inches and its recoil is prohibitive. NATO standard 7.62 really could use the same sort of attention that the 5.56 round has recently garnered.

    Most servicemen/women can’t hit beyond 5.56’s effective range on a good day, let alone in a stress situation. Short barrel 7.62×51 carbines are dumb. In short, I don’t really see where a modular lower would really affect combat performance vs. dedicated DMR rifles, optics and training and an improved 5.56 round for CQB/everyone else.

  • charles222

    7.62mm SBRs are quite superlative, actually-7.62mm doesn’t lose velocity nearly as fast as 5.56mm does out of a short barrel. You can chop a 7.62mm barrel all the way down to sixteen inches and average a loss of just 50 fps as a general rule.

    The other plus side is that even if you are losing velocity, the heavier round can compensate for this-a 147 to 168-grain bullet offers considerably more momentum that even the heaviest widely available 5.56mm round does.

  • Chortles

    @ vereceleritas

    Defense Review seems to give a glowing review for almost EVERYTHING!… doesn’t help that their stories (particularly for weapons) tend to be filled with links to previously reviewed accessories. The pics are great and they I believe were behind some of the only known PDR photos, but the article style comes off as one big shill job.

  • Michael Frangoudakis

    Wouldn’t it make more sense to have one gun in 6.8 Spc. One set of magazines and ammo. Would just need to have a quick change system for the barrel. You could have one barrel in a 10.5 length with a dot sight for CQB and a spare barrel in 18.5 with a maganified optic for long range. You wouldn’t have to worry about mixing up mags or the extra weight of a complete upper. If you carry the extra upper, you have to have some type of specific case to keep the bolt carrier group from sliding out and getting lost/damaged. The 6.8 will do more than the 5.56 and almost all that the 7.62 will do. It is proven for power and accuuracy. If you are carrying two different calibers you will have to choose for the mission what mix of ammo you will carry. You will need two different mag pouch sizes. It’s totally stupid to essentially carry two seperate weapon systems and ammo instead of one weapon and extra barrel. The barrel is shorter and lighter than a complete upper and takes up less space. More room for a soldier to carry other needed gear. One type of ammo is much easier to keep up with and supply to the soldier.

  • my piece of idea is to have a common upper receiver for 7.62 NATO/5.56mm and the serialized lower receiver, all you have is to do is to change different barrel no more extra upper, you just carry lot of ammo I think Colt can do it, what you say and for the 7.62 version the barrel should be 18 inch cold hammer forged polygonal rifling

  • Ron

    The 7.62 round drops like a rock after 200 yards.

    It is only useful for spray and pray hope I hit something combat.

    Does not mater how powerful it is, if you cant even hit an elephant at 300 yards.

    I stick to the 5.56.

  • Pete Sheppard

    Ron, are you thinking of the 7.62×39? I believe most of the post-ers here are talking about the 7.62×51.