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

Steel targets ring, are ya listenin'
On the range, brass is glistenin'
A beautiful sight
We're happy alright
Shootin' in a CQBR wonderland

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Barrel was pre dimpled!

For some reason I can't adjust the gas block when I unscrew it. I think some red loctite seeped underneath the gas block.

Complete gun painted at one point.  Uppers get replaced, rebuilt or second upper swapped (either 10.3" or 14.5")

CD

Hey I don't have to turn tricks to see your pics anymore. Rifles are looking great.

Would be cool to have the tune match steel impacts fired from a Cqbr. Someone in YouTube/Parler land make this happen.

Don't quit yer day job, bruh..

Christmas is over

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CD

Looks like pic of the FOB companion I've seen before.  Perhaps the lesson is just "lay it down, spray it all, carry it a lot, and shoot the shit out of it."

@krdt What?  No junipers with brass ornaments on them?

So simple and clean.

And a joy to carry.......

CD

I'll bet. When I drug my CQBR out from the truck yesterday and holy fuck is that thing heavy.

Yes I agree, BUT, wasn't there an AimPoint T2 on it at one point?  I liked that!

Aimpoint T1
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CD

So I just found this trick out thanks to a pic in the Glock 19 in sf thread (some may be thinking no shit dumb ass)... but a ladder rail panel actually makes a pretty good pressure pad mount when it's flipped upside down.

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Yep, Streamlight's TLR-1 long gun kit comes with a coupla pad mounts that work just that way.

Geaux Tigahs

How do you manipulate the pad and the ATPIAL? Do you "C"-clamp the ATPIAL using your thumb to activate it and then shift your whole hand back to activate the light pad?

Never really used both at the same time. Normally thumb sits right behind ATPIAL and then I just move it back or foward to activate whatever I want. 99.99 % it's the light.

I broke down and used Arfcom hosting; works as long as it's not a serious photo dump.

Thanks... lighting was pretty terrible by the time I got around to taking pics (got out there late and was more focused on getting in some shooting). Had to bust out some heavy-duty PS editing, but whatta-ya-gonna-do? Good chance to play with settings/effects I rarely use.

Lol. I can picture this (and also the nightmare of cutting/pasting/replaying steel impacts endlessly in Premiere ;p).



Christmas isn't over til I say it's over.

Pictures were taken on Christmas Day; what, are you some kind of grinch?



Haha... at least a CQBR Burro with a Santa hat -- something. Must be slippin'.

Considering the rest of 2020, I'd say it was about par for the course. Hell, still being able to create a decent brass pile is a Christmas miracle these days, lol.  

Agree - glad you got some blastin' time. Live your life or they win.
You can get our CQBR Burro next year, I don't think they're unionized.

That upper in 2keylows pic influenced my diemeco upper. 'Cept I painted my rail.

I'm not crying, you're crying

That's.... pretty depressing lol

Real flex

I love this configuration man, super nice!

I've been cheating on this setup. A T2 w/ Ap's magnifer setup has been growing on me.
Once it gets back from AP it will be semi-permeant on this rifle. My ape hands destroyed the helicoils.

The Su230 will retire on a 1.5er.

I definitely know where you are coming from...

This is the way.
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Hey guys i have a few questions:

1) Where can i find a DD MK12 Low profile gas block in stock right now.
OR
If any of you guys have a brand new one you're willing to sell, please email me.
OR
I could trade you for my Colt Teardrop FA

2) What length gas tube do i need for my Colt 10.3" barrel?

3) What length gas tube do i need for my Colt 14.5" barrel?


Thanks

Sorry can't help you w/ the 1st but for gas tube length they are both carbine length.

RKS USA appears to have them in stock.

Finally I'm almost complete

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(Anyone know how I can post these in better quality?)

Looks real good.  What else are you going to do before you call it complete?

I host my pics on Imgur.

I used the upload image function on here I guess it killed the quality of the image. I have an RC2 on order, and I'm going to switch to a surefire flashlight/eventually a PEQ

I’ve owned a few M3X lights but always seem to go back to Surefire.  I’m running an M300C on mine.  One day I’ll pick up a Peq for mine also.  

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I dig it.

Got my surplus mk18 upper kit in today. Little bit of “rust” on the outside of the barrel but nothing that a little CLP couldn’t clean up. Bore looks good and rail had normal use marks on it with some extra dirt. Bolt carrier looks like it could be a fn with a bad attempt at stamping but who knows. Barrel looks to be a chopped down colt, Only markings on it is an 0 and the date of manufacture. Gave it all a good cleaning and got it assembled. Gonna go give it a function and accuracy test tomorrow.

Even though I’m not a huge fan of the overall performance of an eotech I figured I would get another one for this mk18 upper this time. So exps3-0 and G33 are ordered and on the way.

Very nice!! I missed out on this uppers from TA

Do you think the BCG could be a badly marked Diemaco? TA said a few uppers had these in the group.
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Got my TA MK18 kit in the mail as well.  Everything is in pretty good shape.  Other than the C marked BCG, I'm not sure what the other markings mean.  Any idea where TA sources their MK18 kits?

Good stuff.
Barrel looks like an FN Socom profiled barrel. Proof marks denote FN manufacture and M4 feed ramps.
"X7176" is probably a way for the unit to inventory for themselves or the upper was provided to a specific operator.
No idea where TBA picks up their goodies.

Black Creek or Savannah marked? Lot/Date marked rail?


Side note:
Aimpoint CS is legit.
Mid December I destroyed the helicoils with my gorilla strength and they ended up swapping for an entire new unit.

Got mine in. Daniel Defense barrel. C marked BCG. Black Creek rail.

So based on the pics above, it appears the surplus upper kits are shipping with government and socom barrels? Was that a choice option? Or luck of the draw?

No option, luck of the draw only, these are surplus not handpicked, homie.

Heads are gonna explode at those DD barrels LMAO