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).

----------

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.

----------

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

----------

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

----------

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).

----------

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)

----------

Link to previous threads

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

Shiiiiiiitt......I may need to plus up my stash.

So, I got the SBA3 installed and had a little time to mess around with it. The thing I noticed immediately was the weight difference: the SBA3 is significantly lighter than the SBM4. The SBM4 with APF tube comes in at a fairly hefty 17 1/8oz, while the SBA3 with the included tube is 11oz even. On the one hand, the lighter weight is nice and I immediately noticed the difference in the overall weight of the weapon; on the other hand, the extra weight of the SBM4 does help to balance the front-heavy CQBR a little better. If I were running a suppressor, I think I'd probably go with the SBM4.

Another significant difference is that the SBA3 is made out of something more like a hard plastic rather than the usual rubber on other SB braces. The "flaps" are the only part that are slightly rubbery, and even there the rubber is much harder than on an SBM4. The harder plastic/rubber seems like it would hold paint pretty well, so you'd have a viable option if you want to rattle can it - which I definitely like. Very good chance this will go over to the Mod 0 and get a paint job after my stamp comes in.

Between the two, the SBM4 still has a slightly better cheek weld IMO and has a bit more of a solid and beefy feel to it. Of course, that comes at the expense of weight. One other feature on the SBA3 that I definitely do like is that it can't rotate on the tube. While I never had too much of a problem with the SBM4 rotating, during the heat of the summer it did happen occasionally. Also, sorta goes without saying that having adjustability is a big plus - the option to collapse it down when inside vehicles was a big part of why I wanted one to begin with.

Overall, it seems like a pretty solid little brace with some very useful features. I'm definitely looking forward to giving it a try this weekend. And now the pictures :D.

Fully extended:


Fully collapsed:

Noice. I gotta say, aesthetically much more pleasing, and you'll be pleasantly surprised range day. Notice how built up the end of brace is? This was definitely built with much consideration to the end use. With how they've been evolving, I bet the next model will be a full on stock with a Velcro strap. Someday.

Eta- my only concern for the longevity would be the adjustment latch. The plastic seems a little thin and brittle for such a hi ware area. I'm not sure if they re-designed the latch system to avoid looking like a stock or not, but I definitely would've used a different or thicker plastic for the lever/ latch. I'm curious to see if it's been an issue yet.

What?

Attached File

Looks like it's copper/bronze.

Triggered

*sniff sniff* Smells like.......TNVC in this bitch.

With a few changes, I've believe I've now achieved a proper Block I clone.

Swapped Brownells Retro A1 pistol grip to Colt A2
Swapped Wilcox Comp M mount to early model, angled QRP
Swapped Colt ambi safety selector to Colt standard, no-tick selector
Removed CQD FSM (though now I don't have any sling mount up front)

Future plans:
KAC NT4 (black) and possibly a PEQ2

I agree 100%!

I just commented on your IG post.  Yeah, I love my block 1.  Rattle can that...

EDA: Added Pic...

Looks great. And yes... be bold, be one with the rattle can :D.

I just picked up a new Gas Buster in black to rattle can for the Mod 0/Block I. Still might end up using the FDE GB on the Block II, so I just couldn't bring myself to paint it :\.

Very good. I like that!
Just need that side sling swivel. Or 550 cord.

Looks pretty good. I liked the wilcox mount better but either is gtg. If you're going to this level of detail I'd get rid of that gross commercial hot dog safety selector tho.

Lol. Hot dog.

Idk, I like the qrp...just so used to it I guess.

Attached File

Dang it, I also was partial to the Wilcox, but I was going by Page 1 which only lists the QRP for Block I + others had chimed in about using the QRP instead. I’d seriously switch back if either is GTG.

Didn’t realize there was a difference in non-ambi safety selectors beyond tick mark or no tick mark. Can you elaborate?

Thanks.

AFAIK, a true "retro" Colt no tick safety has the bar offset from the center, like this:



Compared to current production - tick or no tick:



However, they both have a "hotdog" thing going on, so I dunno.

Either is definitely GTG and to me the Wilcox is just a more elegant part. They've always been meticulous in their machining. The curves, etc… they're just pieces of art. Both were available for cqbrs, but it's spec for the Mk 18 Mod 0. You'll commonly see SEAL photos from that era with them.



And yeah, see the post above. The commercial colt carbines come with that hot dog safety that has a huge hot dog on it that extends into the middle of the selector and just looks weird.

The psa lower I'm currently using has a psa lpk...
Hot dog.
Lol.

I agree that the Wilcox is more elegant and I would've hung onto it had I known it was also GTG for Block I. All the pics I find have the Wilcox and I don't think I've ever seen the QRP except that one SEAL photo on Wikipedia for the CQBR page. QRP definitely feels more stout, and I've read that guys in the sandbox complained about the Wilcox thumb screw working itself loose frequently, but still I think Wilcox is the better look. #kickingmyself

As far as safeties, I thought tick vs. no tick referred to the presences of a hashmark on the support side of the lever (to point to safe or fire, etc.). The current commercial ones are blank on the support side. Second, is there a non-commercial ambi safety? Because the hot dog piece is present on the ambi safety and looks no different. I agree with you that it's ugly, but I guess I didn't realize there was a military version that was not so gargantuan. To me that top one looks like an old design. Is it fielded and I've just managed to not notice it in any pictures?

sopmod block 1 illumination
Surefire m962  fat body, gen 1 bezel kit with uu07 pressure switch tail cap and sw02 clicky tailcap plus 5 filters
Gen 1 m952 with uu07 pressure switch tailcap.

tanodized g33 is up in the EE.

not mine and not as good of a deal as the last drama fiasco one that was listed

first sentence . I tried Savin you $. twice.

eta- damn she is beautiful!

That you did. Fully admit I should've paid more attention to that sentence. The good news is we're talking $123 and change for a new Wilcox mount from TNVC if I do switch back.

ETA: And thanks!

Nice looking Slasher!

How did you end up with a purple upper? By accident? Is it a cage code upper reciever?

They are both great mounts. I like the three click torque aspect of the qrp, the weight of the Wilcox, and the aesthetics of both. Anyone seen pri mounts in the wild? they are very close in resemblance to the Wilcox in my opinion. not sure I like how the mount appears to have a seem where the base meets the neck.
Attached File


Damn! thats sexy. square forge I take it? those are the only newer ones I've found with purple. that is fantastic. bravo, bravo.

Nah that's a Cerro forge with the CAGE code....which means its a new purple receiver. Sweet

@AZ_SBR

Yes, Colt ambi selectors come in semi-auto (commercial or “hot dog” lmfao) & full-auto (not hot dog).

Semi / hot dog

Attached File


Full

Attached File


Issue ones are obviously not hot dog.

BARNEY!!

I think someone took a wire wheel to this thing to get the paint off.

Ahhh. Small screen, couldn't tell. Even better then. That means purp is still Rollin out.

Those bastards. That's about like the new cage marked 6920 upper in the EE with less than 100rds that looks more beat up than my '05. What's goin on by the gas tube hole? Looks like it was Fde at one point too? Before black?

Not common as most are using the small round FA currently found on M4A1s.  There are some out there.  Looking at one on the rack in front of me right now.  Just got back downrange this week.

CD

A lot of non-sense about not having select-fire lowers.

Yeah, I'd love to give you guys some romantic story about how I obtained some super special purple upper, but in reality it's:

1) Emailed my dealer asking for a colt LE6920
2) Dealer ordered from Lipsey's or RSR
3) Rifle arrived.

The only thing strange was the lower had CRxxxxx instead of LExxxxx.

I'm just glad that after getting the barrel chopped down, my suppressor(s) still align correctly. I've had rifles(new) that line up like shit to the point where I can't attach my suppressor without fear of a baffle strike. ADCO seemed to do a good job on this one and it appears right at 10.3"

My contribution here toward the 10.3" thread. My block ii has some lag time yet. But anyway, humor me.....block iii or frankengun?

P.S. - Stole @krdt picture technique and I gotta say, looks nice!

Solid write up man. I gotta say the thing is far more appealing but it isn't to say that the sbm4 was never that awful looking either. The a3 just refines that look a little more. Glad I ordered one up then. On the other hand I get your counter argument about the weight savings. These guns are front heavy and the scale would definitely tilt a little more with an a3. I've had sbm4 rotation issues too but never been much of a hassle. Let us know how the range run goes with her.

From what I hear colt is having a issues with their anodizing that’s why some are getting odd shades of color.
I tried ordering a upper 2 weeks ago and that’s the reason I got for them being out of stock.

Heh heh. I forgot about our back and forth days.....FDE vs Black EXPS 3-0, teardrop vs small round etc.

Good times man. @KILLERB6

60 wat? Its the new URG-O Mk black -Sorta Improved.....

Can I be MILSPEC today and be that guy
Attached File
Attached File
Attached File
Attached File
Attached File