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

It looks sweet but in my mind it's just not that practical of a setup.

You mean Mk6?
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I

Yeah that and it would be pretty heavy…

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Trust me, I have had the idea of doing this as well…

For someone using a 14.5 and 10.3 combo not very practical.

I wonder about if you were intending to use the 10.3 as a do-all rifle how practical the Razor would be

Razor, you say?

where can I find a replacement knob for an OG Wilcox Aimpoint mount ? mine is pretty busted. thx

Email Wilcox and ask?

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1.5 love
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Greek Frogman
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Oink oink!

Thiccc

I decided to put the push button on my surefire. (Disregard the ambi badger g3 sharping handle. I sold my gas buster, and now I am in need for another one.

I wish the serialized uppers would have been around a few months earlier. I ended up with a Diemaco anchor harvey cqbr-0522 marked upper that I got to replace my current Diemaco. Shitty part is I got the marked upper right after installing the 4p with rocksett and after installing the gas block with loctite per badger ord. instructions. I know there are tricks to getting the 4p off, but im still avoiding it. If I don't do it soon, im afraid the stripped/marked upper will turn into anther block2.
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Are there any mod 0s that were ever pointed with a woodland or multicam coating?  Something with greens and browns?


And is there an EOD clone thread with the OD Green CAS-V?

I just popped the MD off of my EMC the other day that was Rocksett'd on. A reaction rod and a well-fitting crows foot snapped it right off. I did give it a couple of smacks with a brass hammer before but judging by the sound when it came loose, it didn't do anything.

to my knowledge, the casv-elt (fde) were the only ones ever purchased/ issued/ used. I know if you do a google search there are a few figurines or toys with a green casv. I'm not sure why though.

I haven't searched yet, but I remember some ppl soaked the muzzle over night before removing it. I wasn't sure if heat would do the trick? The other day I had a set screw from my gas block almost break an Allen wrench, so I hit it with the propane torch and that was all it needed.

It's a ceramic, so it's highly resistant to heat (perfect for gun barrels). I don't believe the water part, I'd wager that it would have come off just as easily had they not. You'd have to have applied it to 2 different guns in EXACTLY the same manner and have a way of measuring how much force it took to break them loose.

Ok. That makes sense. I don't see how any liquid could even penetrate the rockset to get to the threads, especially water. My thought was by heating up the muzzle device, it would expand just enough independently from the threads, that I'd be able to "break" it with less force.

Eta- I need to get a reaction rod. I’ve been leaning towards the Midwest industries version because it has a “sail” that spreads the forces out more evenly.

I could definitely see heat expanding and breaking the bond, but the heat won't affect the Rocksett itself. I got tired of waiting on a Knightstick (was told 2 months a year ago) so I bought the MI one for 308 just so I could swap out the FH to the MAMS. It's built very well.

The website of the manufacturer of Rocksett literally says a hot water soak will remove it. I’ve seen them removed both ways, but the vast majority have been with a hot water soak.

Interesting. Didn't know that.

What rmr mount is that

Reptillia ROF-90

Yeah I don’t know the voodoo behind it, but it works.

Here is a tech sheet I had rocksett send me at my PD as we in the armory had questions. Hopefully it helps out. Look down at the end for break away instructions.




And a couple quick questions... for all CQBR front sight post variants, including MK18 Mod0, was a Mate h BUIS ever used or a Leupold MK4 CQ/T?
TIA

Yea I've removed several with a half hour hot water soak.

Thanks for the info!

Love it

So I found an interesting cqbr while searching for images. I don't think I've seen this image posted yet, but I may have seen it and forgotten. It has a 7" larue quad rail, an eotech 4x and a grippod to top it off. Has anyone in here had an eotech 4x mag? Curious how good it was. I saw one in the ee a few months back. Attached File


Second guy has an Arredondo magwell. Don't see those on block 2's very often.
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Early sopmod surefire m952 with SW02 clicky cap.
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I wish this image wasn’t cropped. Cqbr with trijicon reflex acog rx01nsn.
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Just a quick note for those interested in breaking Rocksett free on installed MD's... I've done quite a few of them.

The MI URR is indeed your friend. It works better than G's reaction rod as is spreads the torque load into the upper receiver as well. Money well spent.

Truth be told, I stopped doing the hot water soak prior to MD removal. Between the MI URR & and a 1/2" breaker bar they come off like butter.

I've also used Rocksett sparingly as indicated in the letter above. You really DON'T need to add much when installing a MD.

This coming from someone who shoots suppressed exclusively, and the MD's are subject to more torque pulling the can's off at regular intervals...

Never an issue, the juice & proper MD torque works.

Carry on

Matech has been used.  I feel like I've seen the CQ/T on a cqbr in at least 1 pic, but can't find it.

This may have been asked. Are Law Tactical Folders being used on MK18s?

Ive seen a couple of pics of block ii's with the law folder. Combat diver has posted the pics, but I don't have em saved to post.



Someone just got a heck of a deal. A Kac ris in great shape just went for $75 in the EE. Perfect for a mod 0 or block1. I was too late.

They are apart of the URGI program. So you'll find URG uppers with them, yes.

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Magpul rear sight. Nice.

Pic from when I had a 552. I saw someone referring to the 552 as an su231. Is that correct? I thought the 553 was su231 and the eotech exps3-0 was as an su231a. Anyone know if the 552 ever had an su designation?
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That magpul sight will save someone a few bucks.

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Found someone other than Mike Glover that likes to mount their 552 on the arms #54 tall mount. On the left, is an eotech 551 mounted on a carry handle, which is roughly the same height as the arms #54 mount. OG chin weld. Both have a surefire m900, Kac ris or ras, and peq2's.
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That's Kevin Owens... I'm assuming you knew that.

of coarse..

Eta
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Eta- I almost posted a pic of Kyle Owens the wrestler, but decided against that.

I’m not tracking that they’re part of URGI.

URGI- upper receiver group improved. This is the semi new USASOC AFSOC 14.5"/11.5” with a midlength gas system and Geissele rail. The law tactical folder can be found on lowers that are part of the urgi program. From there, 10.3" URG's have been used on those lowers with the law tactical folder. That's what he was saying.

Yeah Should've worded it better, but approved for use with the URG-I would've been better. Obviously not an upper receiver part.

I knew what you were sayin. I wasn't sure if he knew what urgi meant or not, so I tried to break it down.

Thanks but I do know what it is. It’s actually USASOC not AFSOC though, the afsoc thing was a commercial purchase I believe, discussed in a PJ thread around here somewhere.

Ah, got it.

AFSOC uses the URG-Is when attached to USASOC also

I ran mine that way for a bit attempting for a do it all setup since the JM-1 perfectly fit the ballistics out of a 10.3" FN SOCOM barrel.  It definitely makes the MK18 into a brick.  I reconsidered the Razor since I use the MK18 a lot for pig hunting at night, since a T2 on a Scalarworks mount worked well for that and made the gun super handy jumping in and out of a truck to walk up on a group of pigs.