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

Bought my first from them a couple weeks ago too! Unless you're gonna hard core and get the 4 prong AU has the best price on the SF3P that I could find too. $89 shipped.

On another note does anywhere have the KAC taupe FS in stock? My googlefu is showing everyone out of stock. For a block II with an EOTech what is correct for the rear BUIS? The Knights 0-300 or 200-600. Micro or not?

Black are also kosher.  I've installed many as replacements for lost Taupe models.  Both have the same NSN in the system.  Get them both when I reorder.  KAC 0-300 were early block I sights.  Current block II would be a black KAC 600 (non Micro).  Non marked for Army but Marines need theirs to say "USMC" on them.  Other BUIS would be the Matech.

CD

@Dobs013

If you decide you don’t want it I might take it off your hands if it’s the carbine length.  Been thinking about building something with one of those.

Thanks for the info!

i have a used one in the EE if anyone is looking. its totally nostalgic. i built a clone of my M4 with it for 6 months to play with.

Thanks CD - I'm getting ready to order a couple labels from Carolina - did the MK12's ever have labels, or only the MK18's/M4's etc...

It's temping to pick up a 2nd one at that price, as I am always swapping mine back n forth from my MK18 to my M4, but I really should get a Thunderbeast first for my LR.  :)

That’s the one rail I want to have, at some point.  Are there more where you found that one???

Not to get off topic too much but the out of production KAC FF RAS in all flavors are coming back at SHOT.

I’m sure it’s been asked before in here, but is clone correctness the main reason you all grab the RC over other cans (like the Saker, SpecWar, Sandman, etc.)???

I don’t have the scratch right now to buy a can just because it completes a clone, so I’m trying to decide which direction to go.  Just curious if clone correctness is what drives most of the guys/gals in here to the RC.

For me, clone correctness certainly played a part, but it's also a good can at a reasonable price either way. It's sort of a win-win situation... quality can at a fair price and it just so happens to be clone correct choice? Where do I sign up! It's not like you're thinking, "Man, if it weren't for the clone game I wouldn't touch this POS with a ten foot pole." There are certainly clone parts like that *cough* M3X *cough*, but I don't think the RC even remotely falls into that category.

No...haha. I happened to know a guy that got one on a complete 9mm upper he bought and he wanted to change the rail. So I snagged it for 3 hundo

They are but I'm pretty sure they are gonna have the newer laser engravings and they won't have the old school purple ano

With all the G love lately, I guess that Garand Thumb was right.

https://youtu.be/AADEn4OBc34

Me too.  I missed one at $80 5-6 years ago.  300 is too rich for me.  Glad someone got one.

Well you guys have me convinced. Guess I'm keeping it and doing another build. I need to stop looking at the EE when I'm drunk

Blasphemy. If I followed this advice nearly half of my rifles wouldn't exist.

This might be an odd request, I am finishing up my mod 0, and installing the KAC RAS. But I feel like it’s not Mating up to the receiver entirely? Could someone post a close up pic of the RAS where it mates up to the delta ring? Possibly a side and top view?
I’d really appreciate it

Tried to grab a few clear ones below. Let me know if you need another angle.

Hang the rifle muzzle down when you install the top rail of the RAS. Lets just say, the metal hook inside the RAS likes to get caught on the wrong side of the barrel nut. Once it is secured in the correct position, then tighten the screw down.

Yeah, it can be a bit of a pain with a brand new delta ring spring since the position with the most leverage - at least for me - is muzzle up. Generally as long as the barrel is horizontal the RAS barrel nut clamp should drop down below the barrel nut - even better if it's tilted downward. Maybe I am lazy, but I just use a large flathead screwdriver to pop the RAS in. I sit the upper in my lap with the barrel horizontal or aimed slightly downwards, shove the front ears of the RAS in and then use a flathead screwdriver with either some electrical tape or some flannel cleaning patches against the contact points - tip against the delta ring and pivot off the RAS. Usually pops right in with minimal effort.

Really appreciate it fellas. Looks like I had it right the first time. It was that gap that was throwing me off. I assumed the delta ring would come closer to the rail section

That’s perfect thank you.

No problem man. If you look at the section of rail that interacts with the delta ring you see it is tapered. This lets the delta ring push agains those tapers and tighten the rail up under constant pressure from the spring. If those were flat and the ring came right up to the rail section then it wouldn't be as tight and could have some play.

Mine was really tight in the delta ring so I gave the ring a few smack with a soft face hammer from behind to seat on those tapers better.

pretty much what he said... ^^^

Just out of curiosity, what's the going rate for Surefire 4P flash hider/suppressor mounts these days? New and/or used.

ETA - I ask because I have two I think I'm going to get rid of.

+/- $300. They dipped down to around $200 for a little bit, but seem to have gone back up. Still kicking myself for not getting one when they were cheaper.

more Gman spam. because its somehow allowed in here and "correct" winning.

Thanks a bunch.  Hoping for a .070" or close to gas port.  But DD sounds perfect. Thumbs up!

Haven't seen these posted yet. Guy on Reddit posted his buddies deployed CQBR with a personal Vortex Razor AMG holographic sight on it.

Thread 1

Thread 2

the quintessential "we are deployed" picture.

love it.

Shit, somebody better go tell that man his issued CQBR is clone incorrect!

Kind of diggin' the whole boot bands/cleaning rod retention deal lol.

ETA- assuming they are boot bands. Front one looks like boot bands, rear one looks like.....algae ropes?

Which grip is that?  Is it DD?  The vertical foregrip sure looks like it's a DD.

Magpul pistol grip, DD vert grip

Gorgeous. What BCG are you running?

i have run a cleaning rod from the kac drop in rail to the CQD rear sling loop. works great. mk18 sometimes does give me stock cases so ive been known to ram out cases on the line. def btdt.

yeah i see boot bands LOL.

Yeah the pistol grip is Magpul K2 and the front looks like DD.

@AstraPat

It’s a Bootleg adjustable with the KAC E3 bolt.

Preworkout, cope, jerk mags, protein, and xmas lights. All the deployment essentials.

Don't forget the CLP in the spray bottle

MK8 guys click here.

It's a pain in the ass to get SBRs in IL, so these complete Colt Lowers from Brownells will have to do.  Optic for the Mod 0 is still up for debate.

Mk18 mod 0 pistol

No it's not.

Taupe is dope.

Family (iPotato) pic. ATPIAL-C should arrive tomorrow.

Attached File

Ha, I see you know him too! As far as I know, the only person to be disavowed from the Special Forces Association. The guy is an idiot that needs to go away.

What color is that reddish brown on there? I need some of that

Reading is fundamental.  I asked about the optics and the link explained it.  Thank you.