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

Y'all be careful buying 4 prongs now...

That 50-60 dollar airsoft 4 prong works on real guns.

Wheres the best place with the best price on a SOCOM can?

Looking for a Socom 762 RC or RC2.

AU

Just some SWAT cop who drinks his own kool aid on Instagram

He's right. Not the best place... but the best price.

That's where I got mine.. I doubt I'd do any more business w/ them though.

 

That doesn't appear as though it was intended to be for Airsoft. Airsoft AEG and GBB's use 14mm negative and positive thread.
Looks like someone just didn't feel like paying $400.00 dollars for one. What's his name here in the thread made one too. Stoner or whatever his name is.
 

Yeah.........if you don't care about ever seeing it

You ACTUALLY got something from them? Who'd you fellate?

 
OOS anyways. So that's either good news or bad news

6 one way, half a dozen the other.

Shooting on Black Friday... No shopping

Looking for a poster/ad that was posted a while ago. Was I believe MARSOC Marine Raiders. Has a guy with an Mk18 with an EXPS3.0-Tan, I think g33 on it. Anyone have it? I forgot what page it's on.

Could it be this one with the 553? No magnifier though....

Not that one. Yeah crap I can't find it anywhere.
*Edit* Found it... Was this one.






 

I'd assume he has some sort of initials or number on it that he doesn't want on the internet. I know lots of guys who mark their gear.

Helmet goals.

Not a Black Friday deal but hey!
Picked up a used but LNIB EOTech G33.STS-TAN tonight for $325.00, doesn't look like it was ever mounted.
Was supposed to be $375.00 but was missing the box and riser mount. When
the seller said he didn't have the box I made sure to ASK if he has the
riser mount and he said yes. I asked because it was not mounted ON the
magnifier in the pictures he has texted me. When I got there he did not
have the riser and said he misunderstood what I was asking for. He
thought I meant the mount that just connects it to the rail as that
raises it up. Talked him down $50.00 because he felt bad that I was
making an hour and a half round trip for the deal and I was going to
have to "buy" the missing part and screws. Plus I was supposed to get it a couple weeks ago but the dude kept telling me he was busy blah blah.
I just happened to hit my LGS/Smith on the way home to see if MAYBE they
might have one and sure as shit he found one in a bin-o-parts and just
gave it to me, screws and all.



Well I thought it was cool! :)









 

Nah, I already posted about this company a while back.  They make airsoft 4 prongs in the airsoft 14mm and also in 1/2x28 thread.  That video was showcasing their 1/2x28 being fired on a real gun.

Look them up on facebook, I don't think they have a website.

heres their facebook page btw.

https://www.facebook.com/haoptwart/

I may be interested in trying one for the 55 or so dollars they are asking for it lol.

Buy it NOW. Surefire it going to rape them.



 

I hope surefire does rape them. They have to have a patent on that bitch. I also think it's retarded that they call it a muzzle brake. How the fuck is a SF4P copy a brake? Either they don't know the difference, or are avoiding calling it a flash hider to not get sued. I'm going with option number one again. (Retardation)

Think I'm going to agree with you on this one. So many things could go wrong with that if the materials used and quality control isn't on par with what it needs to be. I have no problem with people tossing replica LA-5's or replica WMX200's on their builds as long as they know they are fake but those don't have bullets passing threw them at high speeds.



Some jackass it going to buy some up and pawn them off at gun shows and they are going to get into the market and someones going to end up getting hurt or blow up a silencer when the things out of spec.
 

From the pics on their page, you can tell the difference between theirs and the real thing, because it has a dimple where someone would pin/weld it normally.  Whereas the real 4 prongs don't.

I'm going to get one, test it out with livefire and see how things hold up.  If its worth a shit for 50-60 bucks I think that's not that bad of a deal and could even go on a .22 conversion upper or something.

I have one of the replicas stoner made, need to give that thing a whirl one of these days. I trust stoner's abilities way more than some airsoft geardo.

Also, big shout out to H0AG for the FN CHF CL 14.7 barrel! Thank you brother!! Love me some FN.

HMMMM I didn't think about using one on a .22LR build. I kinda do want one for my Systema PTW Airsoft gun if they have them in 14mm. Actually looking at his FB now, looks like he specializes in Systema PTW stuff.



As far as the dimple, remember... Most people are not as smart as we are! Some idiot would pay like $300.00 for one...





 

With my keen OCD eyes I did notice it was tilted.  From the castle nut to the end of the buffer tube it was tilted up / raised up 3/32 of an inch.  No NOTHING is cross threaded.   The meat of the end plate where the bottom of the castle nut tightens down is thicker then the top of the end plate.  I caliperd it..  SO that is makes it tilt up...  I just want to know

So how much is tolerable of a tilt on the extension tube, and will there be any foreseeable wear problems.   I have a very nice case of OCD and I was about to unsteak the nut and pull it off and take the dermal to the bottom of the CQD where the nut pushes up to it and groove it out.

Ended up selling my real Colt LE6920 M4A1 Carbine marked lower... I bought 4 80%'er's and shipped them off to Braceman a few days ago! Doing 2 M4A1's, an FN and a HK 416.





 

Go on over to a free state and test it for us

I demand pics.  I've been wanting to get some 80%'ers done through him.  Can't wait to see.

Yeah, but is it worth trusting your can to a knockoff that potentially isn't perfectly aligned to the barrel, and/or made out of cheese grade steel? That could introduce baffle strikes and/or the "brake" and the suppressor flying off the gun and down range because of a shitty airsoft knockoff.

I mean, if you call surefire, will they sell you a 4 prong? If they will, and it's 400 american pesos, then just get the 3 prong. It really doesn't make any difference besides street cred, and the only people who are going to notice are the people who know what the fuck they are talking about,....which essentially limits that to people in this thread (myself not included, lol). And if they will sell you one, and you still just really want one, just shell out the cash for the real deal. Peace of mind is worth it imo.


I remember seeing a KAC flash hider that was like $450 and they said right on the page that literally the only reason they couldn't sell it to you for less (say $150) is because they weren't allowed to sell it to the public for any less than they were charging the government.

Which reminds me, I need to get into the government contracting business. Make a note of that. For whatever reason, the government will pay like 5 times what something is actually worth, and they do it with nearly everything. My tax dollars at work.




Can someone remind me exactly what the big deal is with those 80% lowers? I had a friend give me the skinny a couple weeks ago, but it was a basic rundown, and I forget most of it anyway. What are the advantages? I heard you don't need to register it with the ATF, but don't you still need to do that if you want to SBR it? I know I could do my own research, and I probably will anyway, but I just thought I'd ask, as I'd be willing to bet a lot of people in here know quite a bit about it.

Before he gave it to me he made me promise I would never use a suppressor on it, even if I moved to a free state. So unfortunately that's out of the question.

I already have two 4 prongs, this is just something I think would be neat to buy.  I probably wouldn't just go right out and throw a suppressor on it and go to town.

I'd mic everything, check tolerances etc. before I even considered throwing my 556RC on it which is highly unlikely anyways.

I might be on board for one now that you put the whole .22LR  thought into my head. I have a .22LR upper I built from a CMMG upper and a Madbull Airsoft DD M4A1 RIS II.



I still feel as though my concern with them getting into the market and people trying to scam with them is a legit worry. Plus the whole exploding can thing as we mentioned.



 

Pming you.

I'm done with 4Ps.

I pulled the CQBR out the safe after putting it up last week.







Rifle fine.

      Love a dirty girl!

I wanted one for AGES and now that I finally HAVE one, I'm not 100% sure I like it. I kinda wish I had just gone with the KAC NT4 and silencer but now I've paid for a SOCOM and I'm waiting on a stamp... I might just change to the brake+Warden and use the brake for the can and pick up NT4's for all my real rifles and maybe get a KAC can at some point.



The 4P rings like a damn tuning fork like WHOA.



I kinda want the SFCT-556-1/2X28. Love the love of the new closed tine model.
 

The 4P is quiet compared to anything AAC.

I just got a SF MB556K today with my FN barrel. I bet it's going to be hush puppy quiet.

That company says the 4 prongs are made out of 4140 steel.  For whatever it's worth.  That's what I could find out.

4140 can't handle as much heat as 4150 CMV (our barrels are made out of 4150)
But I predict it'll work fine for a while, it will destroy itself quicker than 4150 would though. heat/pressure from rapid firing will eventually wear that bitch out. If you do use your can, I would just watch the firing schedule a bit, assuming it even goes on of course.

Actually they make barrels out of 4140 also. Normally 4140's are chrome lined I believe as where 4150's are not always? Correct me if I'm wrong but I think I remember it going like that.



4140 would be more than acceptable for a flash hider, just don't put a can you care about on that bitch! :)
 

4140 barrels are the bottom feeder barrels. Such as the hundred dollar special companies that are too cheap to use a better MIL-SPEC barrel steel. Generally, the 4140 would be the non chrome lined barrel as its the cheaper option and not as high quality. I think you had that part backwards lol

Hmmm I'm almost positive I've seen some chromelined.
 

Like most topics on ar15, this has been discussed at length:

barrel materials

4140 barrel steel

4140 vs 4150 barrels?

Etc... in summary; the material will hold up fine IF it is actual 4140 AISI-SAE spec. It pretty much comes down to tolerances in that case.

Edited to add a qualifier.

4140 is softer/easier to machine than the mil-spec 4150 steel. Both are produced in chrome-lined variants. Many commercial barrels are produced from 4140 at lower expense and therefore can be sold at lower cost. Most shooters don't know the difference and will never shoot enough to see a difference in performance. That difference is: 4150 stands up to heat mo' betta than 4140 do.

Have you seen this SOCOM series closed-tine muzzle device for sale anywhere?!

...talk about a unicorn

4140 should be fine for an MD, the biggest factor with longevity for those will be what heat trateatment prosses they have undergone and the steel used. If properly heat treated, they should hold up just as well as anything else I would think, however, for the $50 I doubt they use quality steel and they most likely aren't heat treated as its meant for an airsoft application

I would venture a guess that they use pre-hardened 4140. Probably rockwells in the 32Rc range. 4140 is an oil hardening alloy steel.  It's a good tough steel, but it isn't anything like wparkhat SF uses.  They use stainless, just exactly, they won't/don't say...........but I'm betting it is 17-4PH.  That would fit the application nicely.....heat treats in a furnace, air quench, can be hardened to the high 50's if memory serves me, and can be drawn back to whatever spec they would want, probably low 50's.  I have not hardness tested the SF4P I have.......don't know if I want to put on the tester. (it would leave a pin prick divot)

If IIRC, SF uses 404 for their breaks and FHs. Its been a while since I've worked in that shop, but that's what I recall it being.
As for the airsoft ones, I'd be surprised if they are hardened at all as the airsoft application doesn't require it, but none of us can really say for sure.

Someone buy one and send It to Stoner for hardness testing?