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

FF RAS build coming soon...plus some other things

Attached File

It is confusing with surefires 900 series. All 4 of these are m951 at different times in their production. Add an arms 17 mount, and all for become m952. As a kit with all the accessories these become m951xm07. XM = the tailcap and the 07=7", which is the length of the tape switch. Bottom one has an sw02 tailcap.


Add a km3 bezel and m93 qd latch and it becomes an m952v. (Tan one on the right.)

Your new stock sticks out like a sore thumb.  LOL.  Just teasing you.  Nice gun.   Not sure about the sling.  I feel like I see a plethora of sling types in GI pics.

Thinking of spraying this thing....

Great post. Super helpful.

I like it as is. Don't see any black renditions and i think it looks amazing with the shade of that RIS II

Well that settles it.  No spray... thanks Milspec

Wait...what? Milspec saying to NOT spray paint something?

Had to go see if it was snowing outside here in Hell Paso.

Right? Lol. If you think about it tho, all of the guns here are FDE, I think it’s cool to have an all black one. He just needs a black 553 and a black Colt waffle to seal the deal

Tread lightly there rabbit, based on the posts of a few people in this thread your red pill reality could critically endanger their ability to deal rationally with their disconcerted precarious emotional situation. Back away slowly and let them have their safe space.

Not 10.2, not 10.4....10.3!!!!!

I hope you like my Mk18 clone

Where's @10point3 hiding these days? Haven't seen that dude around in a while.

So in other news, I visited Haley Strategic Partners in Scottsdale today because I wanted to pick up a set of their TH1RTE3N sights for my Glock 17 Gen 3 - which they installed at no charge BTW. Their showroom is awesome. There are two racks of fully decked out SBRs and rifles to pick up and fiddle with 'til your heart's content. There was even an MP5 clone. Most everything had laser/aiming devices, lights, optics, and a few had cans, and two had M203 type under barrel grenade launchers. There were at least three FDE RIS II rails - two on CQBR-ish clones and another on an M4 SOPMOD Block II-ish clone. Then they had a Mk18 just sitting in a vise in the gunsmith area. Also got to look through an Elcan Spectre for the first time. Super cool. My favorite part was cocking the grenade launchers (remember: extracting and cocking occur at the same time. As the grenadier opens the barrel assembly...never mind) and pulling the trigger. Because GIJoe. Talk about playing with something you only could dream of. The one in the pic is an LMT LMP somethin' or other. And KAC corn cob. Good grief, that place was awesome. "Hello Travis, can I come hang out with your guns next week? How does Tues from 2-4 pm sound?"

Dayum!
Eta: looks like you had fun @AZ_SBR
eta-picture

Ha!

I attempted to remove the hood on my 552 the other day, and one of the heads are stripped out. Any suggestions on how to remove it? I have replacement screws on hand.

Grind a flat head notch into it and unscrew with a flat head screw driver. If old hood gets cut with it, so be it.

Tig- yes I'm feeling ok lol

That's the way.

Rubber band before you start cutting...

https://lifehacker.com/5462520/remove-a-stripped-screw-with-a-rubber-band

My wife suggested that on a stripped screw on my bike (battery terminal screw) couldn't get it to work.  Resulted in much profanity.

Never gotten the rubber band trick to work.

A LH drill bit will work, with a particularly fucked bolt head, or in the event the head snaps off.

Ahh forgot about that one. Would be worth a shot before flat head route if you want to save the old hood Dyzastr

Yeah, SF doesn't make their naming convention easy to understand sometimes.

That's why you never take advice from the gf/wife in matters like that.

Out of curiosity, what’s the consensus on the KAC grips at brownells? The same grip is listed twice, for $19.99 and $67.99...

https://www.brownells.com/rifle-parts/grip-parts/vertical-grips/ar-15-forward-vertical-grip-prod117515.aspx

Cheap one says "military contractor overstock". Not sure I've ever seen a difference between a "civilian" and an "issued" one tough.

I bought one of the $19 ones.  Looks the same as any other one I've seen.

In that case, a few it is then. Probably not a bad piece to practice cutting down to stubby length before attempting that on my taupe

I've seen the left hand drill bit done b4. I'll prob try the flat head slot first and if that fails, out comes the drill. What would I be rubber banding?
Edit- I see I have it backwards, try drill first, then flat head. I figured if I tried the bit first, that there wouldn't be much chance tryin anything else after that. Still, what's the rubber band for?

Eta: saw the link, misunderstood at first. Definitely gonna start there, then move onto the more invasive procedures

Had the day off yesterday and spent some time fine tuning a couple optics. The new barrel shot really well. It's a 10.3" colt socom profile. I can't remember, are FN the only documented socom profile 10.3"?  The brass catcher makes for quick clean up and if I ever start to re-load I've got a nice supply of once fired brass.

Quick question on receiver extensions ... what would be correct for an early CQBR?
I know that Crane was using M16A1 lowers, obviously switched to a carbine buffer system, and sourcing the stocks from LMT.
Would it be safe to assume they were getting the extensions from LMT as well?

The reason I ask, is that I read somewhere that Colt never supplied more than a 4 position extension in .mil contracts (I assume that's to Big Army ??)
but it seems all the LMT ones are 6 position. Would an early Crane built CQBR (with M16 lower) have a 4 position Colt or a 6 position LMT? Thanks guys. You're a wealth of knowledge!

Just curious as to what you guys think of this.

I'm curious to know what organization or agency this individual is with.

As far as I've seen, only FN has a SOCOM profile 10.3" bbl.  All 10.3" Colts are Govt profile.

CD

Crane would have used standard M4/M4A1 USGI 4 position receiver extensions from whatever Govt contractor.  Here's one

Attached File


CD

3 x 10,3

JSOC early 03-04. Could be CAG based on helmet and ANVIS, but armor looks off. Most CAG guys were wearing OD Paraclete although tri color armor was around in small quantities. Possibly CCT or ST6.

I honestly can't tell, (too stupid to know how to do high res)
Can't see where the barrel shoulder ends and the crush washer begins.  Also, were LMT receivers marked with laser etching back in this time frame? May be good to get a high res close up of that area as well

I can only find one other instance of the image. It appears in June, 2006 in an earlier iteration of this thread (here), where- surprise- pepole argue about whether or not it is 10.5/LMT or not and no resolution is found lol.

Another CQBR "how many licks to get to the center of a tootsie pop" conundrum.

The world may never know.

There is no doubt it is a 10.5" barrel. The question would only be is the guy military or contractor.

Shortest they could go with a bayo lug/KAC NT4 is I believe what the reason was. On the Brit version (made by Diemaco/Colt Canada) I think they did away with the bayo lug so they could use 10" barrels. Which makes sense, because the bayo lug is useless on a 10.anything

I believe the reason 10.5 exists (and existed first) was for half inch increments

Good question. The only explanation I ever found was in this article.