When discussing the Mk 18 / CQBR program, we can divide the history and discussion in to two distinct categories: 1) The weapon system itself / upper receiver supplied and 2) the group of accessories deployed on said weapon systems (SOPMOD).

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Mk 18 Mod 0 / CQBR

The M4 carbine and M16 are not ideally suited for all missions, so it was proposed that the modularity of the M16 series would allow a user to replace the upper receiver of an existing weapon with one more suitable to the task. One of two proposed special mission receivers that were planned for inclusion into the SOPMOD Block II kit, the CQBR has taken off on its own. Like the proposed Special Purpose Receiver, the Close Quarters Battle Receiver has been more or less taken on by the Naval Surface Warfare Center, Crane Division (often referred to as NSWC-Crane or just "Crane") as its own project following the CQBR's removal from the SOPMOD program. Just as the Special Purpose Receiver morphed into the Special Purpose Rifle, and was type-classified as Mk 12 Mod 0/1, the complete CQBR-equipped carbine has been type-classified as the Mk 18 Mod 0.

The purpose of the CQBR remains to provide operators with a weapon of submachine gun size, but firing a rifle cartridge, for scenarios such as VIP protection, urban warfare, and other close quarters battle (CQB) situations. The CQBR is designed to provide improvement over previous AR-15/M16-type weapons in this category. The CQBR is usually issued as a complete weapon system, and not just an upper receiver. The CQBR was once only available to Naval Special Warfare units, but the Mk 18 Mod 0 has become general issue for Visit, Board, Search, and Seizure (VBSS) missions and, as of 2006, for NCIS agents deploying to active combat zones.[citation needed] The Mk 18 is also used by the Coast Guard's Tactical Law Enforcement Teams, Maritime Safety and Security Teams, and Maritime Security Response Team and the United States Navy's Explosive Ordnance Disposal (EOD) Operators.

Wikipedia has a good article with sources on the original CQBR/Mk 18 Mod 0 and its development.

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SOPMOD

The SOPMOD Program Management Office at NSWC Crane, IN, provides standardized, versatile weapons accessories to meet needs across SOF mission scenarios. These accessories increase operator survivability and lethality by enhanced weapon performance, target acquisition, signature suppression, and fire control.

The CQBR itself was originally part of the SOPMOD program as an accessory replacement upper receiver for the M4. However it was eventually separated out into its own project.

SOPMOD accessories for the M4/CQBR originally included things like the KAC RIS/RAS, SOPMOD stock, KAC M4QD suppressor, AN/PEQ-2 illuminator/laser, ECOS-N red dot, ACOG, etc

The SOPMOD program has gone through multiple minor and major evolutions throughout its lifetime. The most significant is commonly defined as "Block II" and included the introduction/replacement of accessories that met the updated needs of operators. The most visually significant "Block II" accessory is probably the replacement of the KAC rail/FSB with the  Daniel Defense RIS II free float rail with low-profile gas block. Other updates include things like the Surefire SOCOM sound suppressor, EOTech RDS (553/SU-231 & EXPS 3-0/SU-231a), LA-5/PEQ ATPIAL, etc

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Link to docs and photo albums

 Presentation on CQBR from Crane
 Operator's Manual for Mk 18 Mod 0
 SOPMOD Program Overview presentation from Crane
 Photo Album of Mk 18 Mod 0
 Photo Album of CQBR with SOPMOD Block II accessories

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Because of the long history of both the CQBR/Mk 18 and SOPMOD programs, it's common to find weapons with various mixed configurations in the field, all depending on what time and unit the weapon system belongs to. Below are a few examples with descriptions to illustrate this.


Example of a Mk 18 Mod 0 in as-issued configuration including: M16A1 surplus lower receiver, SOPMOD buttstock, KAC RIS, KAC M4QD flash hider, Aimpoint Comp M2 in Wilcox mount, LMT rear fixed sight, CQD rear sling plate.


NSW Operator CQBRs with original SOPMOD accessories including KAC M4QD sound suppressor and AN/PEQ-2 IR Illuminator/Laser.


Member of a Combat Camera team with a CQBR with KAC RAS and M4QD flash hider but with other updated accessories from the "Block II" SOPMOD kit including SU-231a (EOTech EXPS 3-0), EOTech G33 Magnifier, LA-5/PEQ ATPIAL, Insight WMX-200.


Good example of "early" CQBR with SOPMOD Block II accessories including SU-231 (EOTech 553) and SU-233 (Insight M3x weaponlight).


Example of a more "modern" CQBR with SOPMOD Block II accessories including the updated SU-231a (EOTech EXPS 3-0) and Insight WMX-200 weaponlight.


Many times certain configurations are common within certain branches/groups. Here a Marine Raider is seen with a CQBR with an AN/PEQ-16 (USMC issued vs. the LA-5/PEQ SOCOM issued ATPIAL) and KAC NT4 suppressor (vs. the current Surefire SOCOM suppressor).

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Building a clone

If you're interested in building a "clone" of a Mk 18 or CQBR equipped M4A1, here is a basic parts list to use as a guide and get you started. This list is not exhaustive and see the * note above regarding personalized accessories.

                       | Mk 18 Mod 0                      | M4A1 CQBR Block I                   | M4A1 CQBR Block II                                      
Lower Receiver         | Mil-spec forged A1               | Mil-spec forged A2                  | Mil-spec forged A2                                      
Stock                  | Gen 1 SOPMOD (Black)             | M4, CAR, SOPMOD, CTR & others       | M4, CAR, SOPMOD, CTR & others                            
Pistol Grip            | A1                               | A2, ERGO & others                   | A2, ERGO & others                                        
Rear Sling Plate       | CQD                              | CQD                                 | CQD                                                      
Upper Receiver         | Mil-spec forged M4 profile       | Mil-spec forged M4 profile          | Mil-spec forged M4 profile                              
Barrel                 | 10.3"                            | 10.3"                               | 10.3"                                                    
Rail                   | KAC RIS                          | KAC RAS                             | DD Mk18 RIS II (FDE)                                    
Rear BUIS              | LMT Fixed                        | LMT Fixed, MATECH, & others         | MATECH, KAC 300m, & others                              
Front Sight            | A2 FSB                           | A2 FSB                              | KAC 99051 BUIS (Taupe)                                  
Front Sling Attachment | FSB Sling Swivel                 | FSB Sling Swivel                    | CQD                                                      
Muzzle Device          | KAC M4QD                         | KAC M4QD                            | SureFire FH-556-RC                                      
Supressor              | None                             | KAC QDSS NT4                        | SureFire SOCOM556-RC (FDE)                              
LAM                    | None                             | PEQ-2                               | LA-5                                                    
Weaponlight            | SureFire M962                    | SureFire M952, M962                 | Insight M3X (Tan), Insight WMX200 (Bronze)              
Optic                  | Aimpoint Comp M2 in Wilcox Mount | Aimpoint Comp M2 in QRP Mount, ACOG | EOTech 553 (Tan), EOTech EXPS3-0 (Tan), ELCAN 1-4x (FDE)

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Link to previous threads

 Previous Mk 18 / CQBR Thread Part I
 Previous Mk 18 / CQBR Thread Part II

Can I post this here ??

.22 LR CQBR build that I chopped, threaded, crowned the barrel, and assembled together so far

Yes

Glad I'm not the only one that did this and used a real 4p lol.

The only thing I haven't done is turned my trainer into a .22 specific form 1 can yet.

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This page is now the .22 LR page

Ha, that is a great idea. Do a threaded endcap with a removable baffle stack for cleaning and that would be an awesome RC lookalike .22 can.

Can't keep the T2 off this thing.  Also snagged a single insight pad to run instead of dual.

I’ve been happy with my Magpul angled grip on my MK18 but that TangoDown stubby just looks so good to me.  
However I seem to recall someone mentioning in this thread that the normal stubby was a pain to get on the DD rail.  Any truth to that?  I suppose I could just go the QD route.

If you remove a couple of the screws that joins the rails together the TD goes on pretty easy.  It's just that piece of rail at the front that makes it difficult, but by separating the rails slightly it will go right on.

ETA: my terminology likely sucks, lol.  Pic for reference. The red dot is the piece of the rail that makes it a pain to get started.  If you loosen up some of the screws (like shown in purple circle) the rail will drop down away from the piece in the way, and you'll be able to slide it on easily.  After VFG is in place just tighten back up the screws you removed.  Piece of cake and a flat head screwdriver and a couple minutes was all that was needed.

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It sucks, but is totally doable.

I have VFGs on nearly every rifle now (long and short) and position them to be a handstop instead.  Give it a try!

Using the TD Grip Chips is key. Removing the rail is one way, or just muscle the grip on. Set the rifle upright on its stock, angle the grip over the bottom rail's protruding edge and push the grip downward toward the receiver.

Edit- removed possible airsoft image.
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Airsoft alarms are blaring.

Those front screws are just storage screw locations, the ones further back are attached to the bottom rail.

Thanks for pointing that out.  Angle I took the pic at was the best I could do at the moment and didn't show the other screws.  I remembered they were flat heads as well so just circled that one figuring if he takes enough of them out the rail will come loose eventually

Thanks for the help, and the picture!  

Is that some filter in software that you run that photo through to get the pencil-etching effect?  Pretty cool.

Lol. I definitely got that feel, especially with the background. It's a re-post from a "dd ris ii" thread. With the dust cover closed, I wasn't 100% certain. He even has ear plugs in his stock.

Edit- this is to make up for the possible airsoft pic.

Vltor modstock and teardrop forward assist.
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These appear to be simunitions.
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Having the QD model can definitely be handy in certain situations -- beyond just the one-time install. For example, if you want to shoot off sandbags or use a turret for zeroing or load dev, being able to quickly remove your VFG for a flat resting surface and then easily reattach saves a big pain in the ass.

All my TD Stubbies are QD for that reason.

Hey, has anyone upgraded their Comtac IIIs for Comtac Vs? Did you feel like it was worth it?

Thinking about getting some Vs, but it'd be nice to hear some opinions from those that have already made the switch. I figure it'll cost me less than $100 if that makes a difference to the "worth it" angle. Is sound fidelity noticeably improved?

Not strictly clone-related, but I know a lot of us in here run Comtacs.

I do not have the V's (I have comtac iii's also) but I have heard more than a few accounts of high pitched ringing in one ear right out of the box. Just something to be aware of/ research before pulling the trigger.

Thanks for the heads up. Admittedly, I haven't done a ton of research yet, but I hadn't heard that, so good to know.

I have a set of Vs.  While I never owned IIIs and can't compare them, the Vs are very comfortable and I find nothing lacking from the sound.  I have used them at multiple classes and don't even realize I have them on most of the time.

The downside is that they do not work with my TYT MD-UV390.  I have friends who successfully use their Comtac IIIs with the same radio, Disco32 adapter, and Peltor PTT - so the issue seems to be something with the Vs.

I have comtac IIIs, AMPs, and Comtac V.  The V is night and day difference better in audio quality over the IIIs.  After wearing Vs for a few minutes and going back to comtac III you will think your audio is muffled.

I really like the way the original Modstock looks. I'd love to pick one up.

That's just the tinnitus sneaking through.

Wow, that big of a difference, hey? I may have to snag a pair then.

And as an added bonus, I'd finally have some Comtacs in proper Coyote Brown, lol. I got my IIIs at a great price, but the choices were Foliage Green or Black. I ended up liking the FG more than I thought I would, but I definitely would've preferred CB.

Which KAC rear sight do I want for my MK18 Mod 1?

Big noob Kac 300m or 2-600m
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Thanks for the input fellas; picked up a pair of Comtac Vs that should be here Monday.

Also grabbed some standard 3M gel cups as well as the "Prohear" brand on Amazon to give them a comparison -- they were reviewed really well, so I'm curious to give them a try. Obviously, haven't installed them yet, but they arrived today and look promising as possibly an improvement on the 3M cups. They are still nice n' squishy, but are slightly more firm -- assuming they're just as comfy, they should hold their shape longer. I'll give them a go once the Vs get here and we shall see.

Am I gonna get dragged across concrete for this spare parts build ?



How far off an I?

@tinycrumb Rad builds don't get enough recognition in this forum. This clone build is awesome. We need a "Like" button.

I noticed you and Call Sign Ninja @mnrideshonda run LMT extension tubes on your builds--the gray Teflon coated exterior is unique to those. My Colt 4-position extension receiver is out of spec and every stock I've tried is loose and rattles. I've been wanting to track down one of these LMT receiver extensions forever and they finally just become available on their site again.

Link

What is your O.D. measurement? It's possible it's out-of-spec, but it could just be at the small end of allowable spec.

I measured several of my Colt 4 pos, and got 1.1495", 1.149", 1.149" and on the worn smooth RC host, 1.1455" -- those were all unpainted to eliminate that as a variable. An LMT Gen 1 fits almost perfectly on 1.1455" -- i.e. no wiggle, but still adjusts smoothly. The LMT on 1.149" is a bit on the tight side for my preference -- still adjusts, but can take a little effort and/or get stuck with a new extension. Also, I don't think any of them are 100% perfectly round and they may have tiny high points -- be it finish or imperfect machining -- that can make the fit seem tighter on one than another, even if they both measure the same centered from the top with the extension alignment rail at 6 o'clock.

Edit: Guess you already sold it so it doesn't really matter, lol.

I measured specs with a cheap-o digital caliper from Harbor Freight and fed the various numbers to a really helpful dude at B5. To your point, it was on the low side of what was acceptable in terms of mil-spec. So not technically out of spec and for the average gun guy, fine. I just couldn't get the tight fit I was used to with other Colt receiver extension and CTR or B5 Gov SOPMOD stocks I've owned.

Yeah, the extension on one of the Colt Govt Property lowers I picked up recently is actually a good bit tighter fitting with an LMT Gen 1 than I prefer. Funny enough, the same stock fits better on the NT4 host extension that technically measures larger at 1.1495" and on the other Govt Property lower that measures the same at 1.149".

You can see the high point drag mark that's causing it, so you also have the variable of them not being 100% perfectly round to factor into how a particular stock is going to fit -- and even have two extensions that measure the same yet fit the same stock differently. Basically, short of having half a dozen on hand to try, it's gonna be entirely luck of the draw.

For the tight one mentioned above, I'd wager it will smooth out with use regardless.

It's slowly become less of a clone over the years, but I still love this rifle

Rc2

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First clear pic I've seen. Sweet.

Anyone know what units were issued Su-269's? Elcan is the only clone optic I do not have and have not tried, kind of have an itch for one..

Ives seen some non-high speed navy unit with one. I know people have said recon uses them but I've only seen one pic of recon with an elcan and it didn't look like it was su-269 marked

Google is telling me force recon issued them, but that could be some random guy on the internet justifying his purchase. 269 is black, 230 is tan.

TACP unit purchased them for issue in around 2009-2010.  I will look through pics to see if they were 269 marked.  I deployed with one 2012-2013.

@sbye

What offset light mount is that?

Not op, but it's the surefire rotational picatinny mount that comes with the pro series I believe. Comes in mlok too.
Surefire pro scout series

@alpha0815 This is correct. It's the Surefire M640DF Pro and it comes with that pic mount and an mlok mount.

Nice! NGAL and fde Surefire Scout Pro Vampire (at least from what I can tell). Someone with the parts should throw a clone of this together.

Thx dude, appreciate it.

I honestly forgot that I used those, but you're right, I do remember picking a few up like 10 years ago and put them on some of my lowers. I think at the time I was frustrated with 4-position tubes because the sopmod stock is so long that with kit on I needed a position between 1 and 2. They've just sort of been on my lowers ever since. They do seem to fit most of my stocks pretty well.

Members of U.S. Naval Special Warfare Task Unit Europe (NSWTU-E) gear up for night-time DA (Direct Action) training alongside Croatian SOFCOM – Zapovjedništvo specijalnih snaga (ZSS) during Exercise Trojan Footprint 22 in Split, Croatia, May 8, 2022