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

I shall not be infringed by your moderator powers.

Cheers and Happy 4th everyone!

That came together good man, Happy 4th.

Alright, that's quality shit. lol'd.

Losing mod status in 3, 2, 1...

Attached File

What's the best price an nt4 can be had for? They are still up there right?

Just don't drink and post

@Mister_Donut

Good looking rifle! Curious what the weight is? I have a 10.5” that I have a DBAL, SakerK, surefire, and ACOG with MRDS that is just over 9lbs unloaded and want to see how it stacks up to the mk18s

Sounds like a jobs for @Combat_Diver - CD any chance your'e seeing Pri GB's with Combat/Serrated latches out there?

You're not going to do much better than around $1,350.

That FSP RIS II though, shiiiiit that is sexy.

I'm interested as well

Dang. I like them better. But that's alot.

Totally agree with you there.

True, they're expensive... but with RCs showing up at $1,600, they may actually become the less expensive clone correct option eventually, heh.

If the choice is between an RC at $700 and an NT4 at $1,350, it's pretty easy to go with the RC - when it starts becoming an RC or even RC2 at $900-$1100, plus a 4 prong at $300, things become a lot more cloudy.

This is true. I have two 4-prongs that cost roughly $300/each, so $600 total. Two NT4 mounts cost roughly $75/each. So the difference in just the two mounting devices is $450.

I wish I had just jumped on the NT4 from the beginning. Probably would have cost roughly the same in the end.

Yes they do and excellent point. So the difference in the two mounts is closer to $525.

No way I'm buying a 4 prong and I wouldn't pay more than 700 for a rc or sb. I'll be running my sandman for the time being but I need some more suppressors. I feel like the rcs are not made well. Do they work, yes. But strikes, erosion, build up etc just turn me off. Are there any issues with the nt4?

I will just tell you flat out that's nonsense. The RC is extremely well made - tough, low back pressure, little gas leakage and one of the best mounting systems out there.

I don't think erosion is any different than any other can made with similar materials - it's just that RCs tend to be used on short barrels with prong flash hiders and have been well documented with pictures. People also mistake cosmetic erosion with actual damaging erosion. In reality, the RC has a quite thick Inconel blast baffle  - I'd estimate it's twice as thick as the NT4 blast baffle. Naturally, some of the baffle thickness is offset by the 4 prong causing more targeted erosion, but if you used an SFCT to be comparable to the M4QD, I wouldn't be surprised if an RC could last as long as an NT4, maybe even longer due to the thicker baffle. If not, the RC has the huge added benefit of being able to be rebuilt.

The RC does have a tighter bore than the NT4 and the occasional baffle kiss happens, but it's usually entirely cosmetic. I don't hear of many RCs needing to rebuilt because of a legitimate strike. As far as carbon buildup, the shape of the NT4 baffles actually lends itself to faster accumulation (and my limited testing backs this up - the NT4 was accumulating weight quite fast). You can see why it'd pick up weight below:



I would say in a purely pragmatic comparison, the RC is probably superior to the NT4 in many ways (better mount, less gas leakage, less back pressure, lighter, etc.). But they are both very well built, tough cans.

I have a real and a "copy" of the 4-prong and I didn't pay more than $70 dollars for either BUT if I was forced to pay more than $125~130.00 for a SF flash hider I'd just by the closed-tine Warcomp or 3-prong and call it good. It would be covered by the can most of the time anyway.

Ah I forgot about that picture. That's terrible. I do like the fact that guys are getting their rc rebuilt for a reasonable price.

All this talk of the NT4. The wait begins. Check hasn't even been cashed yet.

Attached File

Here's another pic, not sure if it's an RC but it is a surefire.
Attached File

Just the standard PRI M84 Gas Buster.  Next rotation shortly should have the Geissele Airborne charging handles on the URGIs.

CD

It's a 212; you can tell by the end cap weld location.

78Staff is non-compliant lol...

Thanks :)

That is sexy.

Would I be banished from the clone community if I just got a Turbo K and sprayed it FDE?

I dont have a clone correct can either. :/
But eventually, I will.

Yep.

I had a feeling

They say that about 10.5 barrels, hotdog selectors, incorrect sights and stocks. But we get those all the time.

I nominate you the new clone moderator then.

We had an old one??

CHINASPEC556.

Never heard of her.

Which 45 degree Surefire Scout mount will work with the ATPIAL? Thinking about ditching my Unity Tactical micro hub.

Always been a fan of Arisaka products.



https://arisakadefense.com/collections/frontpage/products/side-scout-mount-picatinny