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

Need that. Any more nt4 s trickling out or are they all the new style.

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nav LA5 nice

Coronet and Badger in the EE HERE

If I didn't hate taking off the rail so much I'd buy the Coronet and swap out my Badger.  

Any black exps with tan NT4 pics floating around?

That combination has to exist but less commonly in CQBR pics. Such a combo evoked Force Recon Marines and their M4A1s and HK416s:

If you check the force recon thread you'll find them in there.

Yea looking for one on a MK18.

No tan nt4 but has the correct muzzle device
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Hell yea thanks man. Just debating on how I want to build this one. Don't really wanna do the traditional all fde accessories, I want to mix it up a little some black some fde.

I was originally thinking Micro on LT mount but now am debating on a black EXPS.

Been drawing some inspiration off these.

It’s hard to go wrong with the T2.

The top two are the same Marine.

here is more of his kit.

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That flipped riser is interesting.

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Two I just posted have a MaTech and KAC 600m BUIS.

A couple more pieces

CQBR upper. I finally have the DD Brown and KAC Tan combo.


Still debating on optic. It's so light without the can T1 is tempting. Though EXPS is king on a CQBR

Suppressor approved!

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Couple days off.

Are the RC suppressors (not RC2) still available for purchase anywhere?  Are they still in use in the mil or have they switched over to the RC2, or something else?

RC's haven't been available since Big Tex blew them out in July of 2019. You even got a "SOCOM" code to use for an additional discount! What a time to be alive. They are still in primary use in the mil.

Thanks.  I guess I’ll just watch the used market or eventually just settle for an RC2.

That's the proper way to use a larue riser with red dot/3x combo.

I'm picking up some strong 1980's playboy photo shoot vibes with the fogged lens


I'm proud to say I was a part of that Big Tex sale along with brownells sale of virgin colt m4 carbine lowers. IIRC, after the discount, those surefire RC’s were in the $749 range.

on a side note, picked up a surefire m720v at an excellent price. That last photo dump got me to finally get one.


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So with the new "Approved" accessories... What brand/models are the QD swivel attachments?

Lookin to ditch the HK hooks and go qd on all rifles.

There was just a thread about QD failures and getting away from them.


ETA: https://www.ar15.com/forums/AR-15/Major-QD-Connect-FAIL-/118-781501/

Does this count or is it too modern and not clone correct

DD MK18 pistol to SBR
T2
Scalarworks mounts
SSA trigger
SF mini scout and tape
SF RC2
mbus pro buis
Vtac sling mt
BF sling
Radian safety

Shoots awesome and is very fun… but may not be a worthy mention to the thread Attached File

Anybody know what add on magwell this is?

@WilsonCQB1911 Might be HRF Concepts

Man I wish I wouldn't have hesitated back in 2019. I'll have to live vicariously through you guys with the corncobs.

Looks way too pristine.

It’s been sprayed only once…

Best change that.

I might spray my cqbr .22 trainer again but this one will stay like this for a while.

Pic thread:
My lab is fascinated by deer.

Do we have any ITW pix of the Surefire M340V Scout Pro?

Sorry if this has been asked before. I went back to 01/01/2023 in the thread before asking.

Todays work
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35 minutes later, properly torqued, assembled and headspaced.
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More enjoyable than my day plan.

I thought this image was interesting. Looks like a Leupy 3.5-10

Green Berets

I like it.

SF been doing pack mule courses on and off for decades.

Yep, I’m a dumbass! One of my worst regrets.

Looks like an A2 FH also.

There was a time when unit armorers were building them at the Groups just ran out of SF4Ps and put on A2s.

CD,

what kind of barrel did you use in that build? Looks like a HBAR with 203 cuts, but used to have a FSP. Is Crane cutting down Colt HBAR 14.5 now?

Standard M4A1 14.5" SOCOM barrel (Colt,02/16) that Crane cut down, removed FSB and dimpled.  Just old new stock in shop.