CQBR Block II Clone Build Guide: The Daniel Defense Upgrade

The CQBR Block II is a 10.3 inch Colt upper under a Daniel Defense rail that runs almost to the muzzle. Clone builders call it the Mk18 Mod 1, a name we couldn't find in any primary document.

Most of its parts are still sold, so you can build a close copy with a semi auto lower, a commercial laser and a stand in light.

What a CQBR Block II clone copies

You're copying an upper. Units bolted CQBR uppers onto M4A1 lowers they already had, and the Navy fielded complete carbines as the Mk18 Mod 0.

The Block II swaps the Block I's Knight's Armament rail for Daniel Defense's free floating Mk18 RIS II, with a low profile Mk12 pattern gas block under it and a folding front sight on top. Around it went SOPMOD Block II sights, lights, lasers and, from 2011, SureFire suppressors.

Mk18 Mod 1 or CQBR Block II: what the name means

CQBR, the Close Quarters Battle Receiver, is the upper, and the Navy's complete carbine on it was the Mk18 Mod 0, in our Mk18 Mod 0 clone build. Block I and Block II are SOPMOD accessory generations.

SOPMOD's 2006 and 2007 briefings say "CQBR (Mark 18)" and "CQBR (Mk 18)", never Mod 1, and owners doubted the name by 2010. One retailer relays an unsourced claim of "Navy 18-1" markings, so treat Mod 1 as a nickname until someone documents one.

If you see "M4A1 CQBR Block II", it's the same upper on an M4A1 lower. The 14.5 inch carbine is our M4A1 Block II clone build.

The Block II upgrade program

Crane's May 2003 briefing lays out the upper. The barrel was cut to 10.3 inches, the shortest that still took the Knight's Armament can, per Small Arms Review. The gas port went from 0.062 to 0.070 inch, with a five coil extractor spring, new gas rings and an M4QD flash hider. The lower wasn't changed.

Block II came from SOPMOD, the special operations accessory program, whose 2006 plan ran Block II fielding from 2005 to 2010. SOPMOD's May 2007 list of Block II and phased replacement items gives stock numbers for the SU-230 Elcan, SU-231 EOTech, SU-233 light, LA-5 laser and a second generation rail.

The history behind the RIS II

Three competing RIS II contracts went out in March 2005, to A.R.M.S., Daniel Defense and Knight's Armament. The goals were a floating rail, a floating grenade launcher and better accuracy, and Daniel Defense says it designed the RIS II for that M203 requirement.

Daniel Defense won. A May 2009 Crane notice for a sole source contract said the RIS II had been fielded since May 2006, though it covers the 12.25 inch M4A1 rail. The short rail's stock number, 1005-01-548-1385, dates to 9 February 2007. Only its Daniel Defense part number, DD-8020, and Wikipedia tie it to the Mk18.

Block II milestones, 2005 to 2015

Who carried the Block II

Three groups are documented: Navy SEALs, Army Special Forces and Marine special operators. We found nothing that confirms Rangers, Air Force special operators or Navy EOD.

Naval Special Warfare

The best reference we found is the Navy photo on this guide's hero card, whose file is dated 16 May 2011. It shows an FDE Mk18 RIS II, a tan EOTech labeled SU-231/PEQ, a tan ATPIAL style laser, an Insight light, a four prong flash hider and a black CAR stock.

In 2014 the layout was still in use, painted white.

A Navy SEAL during winter warfare training on 9 December 2014 carries a winter painted 10.3 inch CQBR on a Mk18 length quad rail, with an EOTech, an ATPIAL style laser, a four prong flash hider and a vertical grip. U.S. Navy photo by Visual Information Specialist Chris Desmond, public domain, via Wikimedia Commons.

Army Special Forces

Jeff Gurwitch, who served on Army Special Forces teams, wrote the most detailed first hand account we found, for SWAT in 2017. One of his captions, dated 2015, lists an Mk18 with an SU-230, EOTech MRDS, LA-5 laser, WMX200 and SureFire SOCOM can. For an SF clone, that's your shopping list.

Marine special operations (MARSOC)

MARSOC photos show the black version. A May 2013 DVIDS photo shows Marine special operators with short uppers on black quad rails that look like Mk18 RIS IIs, one with a PEQ-16 type laser. It can't prove the rail maker or barrel length, so if you build a MARSOC clone, you're working from it and owner charts.

Marines of 1st Marine Special Operations Battalion train for visit, board, search and seizure off Coronado, California, on 20 May 2013. Their short uppers ride on black quad rails that appear to be Mk18 RIS IIs, the MARSOC variant. U.S. Marine Corps photo by Staff Sgt. Robert Storm, public domain, via DVIDS.

What changed from Block I

Everything behind the barrel nut carries over from a CQBR Block I clone build. The rail, barrel nut, gas block and front sight change.

Mk18 Mod 0 vs Mod 1 differences, part by part

Here Mod 1 means the Block II setup the nickname points at.

Why the front sight base came off

The RIS II runs almost to the muzzle, leaving no room for a front sight base. A Mk12 low profile block goes under the rail and a folding sight on top. The 2011 NSW photo shows no sight base. Nobody has documented whether issued uppers got new barrels or converted Block I ones.

Which Block I clone parts carry over to a Block II

The complete parts list

Here's every role on the rifle, what was issued, how strong the evidence is and where it comes from, cross checked against one enthusiast parts list.

The CQBR Block II parts we stock, laid out overhead. The product photography is supplied by the listed merchants through their affiliate feeds.

Upper receiver group

Get these seven right and your upper reads as a Block II.

Upper receiver: Colt M4 flat top

Small Arms Review says Colt was making complete CQBR uppers by 2008, and clone lists want Colt keyhole, square or CAGE code forgings you can't check from a listing. Colt's upper is out of stock, so LMT's is the equivalent and Wilson Combat's the budget pick.

Barrel: 10.3 inch chrome lined, 0.070 inch port

Crane's spec is 10.3 inches with a 0.070 inch port, and Small Arms Review adds 1 in 7 twist and chrome lining. Nobody has named the maker of Block II era barrels, though one owner reports Daniel Defense barrels on SF uppers.

Colt's M4CQB is your closest match, though no listing states its port or says whether it ships with a front sight base. The Daniel Defense card is the reported SF variant, the Ballistic Advantage the budget pick. Wikipedia's uncited list puts buffers at H to H3.

Gas block: Mk12 low profile, Badger or Daniel Defense

Daniel Defense pairs the RIS II with its Mk12 low profile block, and clone lists add Badger Ordnance's. Neither maker is documented on issued rifles, so both are pattern matches. You'll need a carbine gas tube too.

Muzzle device: KAC M4QD or SureFire SOCOM 4 prong

Crane named the KAC M4QD, which clone lists call the NT4 flash hider. It's one part, KAC 93048, and it's in stock.

From September 2011 the contract part was SureFire's FH556-215A. SureFire says it developed the FH556RC for that trial but never says the numbers match, so that card is an equivalent.

Handguard: Daniel Defense Mk18 RIS II in FDE

This rail makes the clone: 9.55 inches and 14.1 ounces, free floating and bolted to its own steel barrel nut with six bolts, with a removable lower section. Buy FDE, part 01-004-08020-011, for a Navy or Army clone and black for MARSOC. The 12.25 inch M4A1 RIS II isn't interchangeable.

Bolt carrier group: M16 profile, Colt or FN

Crane's changes matter more than the maker: a five coil extractor spring, one piece gas rings and an O-ring over the extractor spring. Clone lists say Colt or FN, neither in stock, so BCM's M16 carrier plus JP's one piece gas ring is your equivalent and Phase 5 the budget pick.

Charging handle: GI or PRI Gas Buster

No document shows the issued handle, so a GI handle is the safe pick. The enthusiast list names PRI's Gas Buster with the military latch, and we stock that one in FDE.

Lower receiver group

Nothing on the lower changed for Block II.

Lower receiver: Colt A2 profile, semi auto for civilians

The issued Colt M4A1 lower is a machine gun, and the enthusiast list specifies a Colt A2 profile lower with a UID label. We have no Colt semi auto lower in stock. The H&R with military style markings is your equivalent, and the PSA A2 lower is the budget pick.

Trigger: select fire issued, Geissele SSA for civilians

The issued group was select fire, and Soldier Systems Daily reported Geissele's select fire SSF in SOCOM use by 2011. Geissele calls its SSA-E the semi auto only version of that trigger, so it's your closest stand in. The SSA and a mil spec group cost less.

Stock: LMT SOPMOD, Colt CAR or Magpul CTR

No single stock was issued. The 2011 NSW rifle has a Colt CAR stock and the 2014 winter rifle a SOPMOD style one, and Small Arms Review confirms LMT's SOPMOD on CQBRs. The enthusiast list adds the Magpul CTR. The B5 is a budget CAR lookalike.

Grip: A2, Ergo or Magpul MIAD

Only owner lists cover the grip, and they name the A2, Ergo and Magpul MIAD. Any of the three is defensible.

Trigger guard and rear sling mount: GI and CQD

The enthusiast list gives a GI trigger guard and a CQD rear sling mount. PSA's USGI trigger guard is in stock and matches the GI pattern. We don't stock a CQD mount, so this end plate is an equivalent.

Sights and optics

The SU designations are military, so you're buying commercial versions.

Front sight: KAC 99051, taupe or black

Knight's Armament's folding M4 front sight, part 99051, sits at the front of the top rail, and owners name the taupe one. Both colors are out of stock everywhere we track. The Troy is a lookalike.

Rear sight: Matech or KAC folding

No document ties a rear sight to Block II. The enthusiast list names Matech and KAC, and the AR15.COM chart names the KAC 300 meter. The Matech is in stock, the KAC 300 isn't, and the 600 meter KAC micro is an equivalent.

Optic: EOTech 553 or EXPS3-0 with a G33

The 2011 NSW rifle's EOTech reads SU-231/PEQ, the 553 pattern, and the later SU-231A matches the EXPS3-0. SOCOM carried SU marked units, so you're buying analogs either way. The G33 card leads because the magnifier is exact. The 553 is listed but was out of stock on 27 September, and the EXPS3-0 is an equivalent.

Optic: Elcan SpecterDR 1-4x with a mini red dot

The SU-230 is Elcan's 1x and 4x SpecterDR, with a Docter or EOTech MRDS on top per SOPMOD's 2007 list and Gurwitch. Both commercial SpecterDRs are equivalents, and we don't stock either mini dot.

Optic: Aimpoint T-1, T-2 or CompM4s

The enthusiast list gives a CompM4s in a GI mount with a lower 1/3 spacer, or a T-1 or T-2 in a LaRue mount. The T-2 is in stock. The CompM4s has no offers today, so the Army M68 CompM4 stands in. LaRue's LT751 mount is in stock for the T-2, and we don't carry a T-1 yet.

Light, laser, suppressor and foregrip

Two of these you can't buy as issued.

Light: Insight M3X, WMX200 or a SureFire Scout

The Block II light was Insight's SU-233, the M3X, and the WMX200 replaced it in late 2010. Both are discontinued. SureFire Scouts were unit or user additions, so the M640U is your stand in and the Streamlight a budget lookalike.

Laser: LA-5 ATPIAL, PEQ-16 and civilian stand ins

SOCOM used the LA-5/PEQ ATPIAL, its version of the PEQ-15, and Marine rifles the PEQ-16. Neither military unit is sold to civilians, and the commercial ATPIAL-C is out of stock. We found no evidence the in stock DBAL-A3 was ever on this rifle. The Holosun is the budget pick.

Suppressor: KAC NT4, then SureFire SOCOM

Early uppers ran the KAC QDSS-NT4. From September 2011 the contract can was SureFire's FA556-212-DE, which owners tie to the original SOCOM556-RC without SureFire confirming it. KAC's NT4 is listed in black and flat dark earth, both out of stock on 27 September. The newer NT4 PRG is in stock, but it isn't the issued can, and we couldn't confirm it fits the M4QD hider. We don't carry the FA556-212-DE, so the RC2 card is a later generation. Since October 9, 2026 a can needs no federal approval, but check your state.

Foregrip: TangoDown, KAC or Magpul AFG

Model varied. The 2014 winter rifle has a vertical grip, and the enthusiast list names TangoDown full size or stubby, KAC and the Magpul AFG, plus a "Lanco Tactical Gripstop" we couldn't identify. KAC's grip is listed but was out of stock on 27 September.

Front sling mount: CQD on the rail

Owner lists put a CQD mount on the rail. We don't stock one, so the Magpul RSA stands in.

CQBR Block II variants over its service life

The Block II was never one fixed configuration, so pick the year and unit you're copying.

FDE and black Mk18 RIS II rails

FDE is the finish the 2009 notice names for the M4A1 RIS II, the color owner charts give the Mk18 rail and the one on the 2011 NSW rifle. MARSOC's black rails are the documented exception. The Reptile House's 2016 roundup adds user fitted Troy, Samson, Centurion Arms, JP, GG&G and VLTOR rails.

Block II kit on Block I rails

Many uppers kept the KAC rail and front sight base while taking Block II accessories. A November 2011 Navy photo still shows an EOD technician's short upper with a KAC rail and fixed front sight base, and the Block II accessory mix turns up in our M4A1 Block I clone build.

Army SF rails that arrived in 2014

Gurwitch wasn't issued a RIS II until 2014, and got the uncut version in fall 2015. His was the FSP model, and Daniel Defense's only documented FSP rail is the 12.25 inch M4A1, so which upper got it is unclear. Either way, rails reached some teams years after 2006.

What came after the RIS II

The Army's 14.5 inch M4A1 moved to USASOC's URG-I with a Geissele Mk16 rail, in our M4A1 URGI clone build. The Reptile House assesses that Air Force special operators run 10.3 inch uppers on 9.3 inch Mk16 rails. We found nothing on the NSW successor.

What you can buy today and what is unobtainable

On 27 September 2026, 11 of the 22 roles in our parts list had the exact part in stock, three of them generic pieces like the A2 grip.

CQBR Block II parts in stock on GPP today

You can order the parts that define the upper today: the FDE RIS II from $516, Colt's M4CQB barrel from $280.79, the KAC M4QD from $75 and both Mk12 blocks. The KAC front sight is the exception.

Close substitutes and catalog gaps

Commercial versions cover the trigger, both SU optics and the contract flash hider, and the RC2 is the nearest can. The EOTech 553, KAC NT4 and KAC grip are listed but out of stock, and we don't stock Docter or MRDS dots or CQD mounts yet.

Parts no retailer can sell you

Select fire parts are machine gun parts. The LA-5, PEQ-15 and PEQ-16 are military power lasers, and the Insight lights are discontinued. The FA556-212-DE and the original SOCOM556-RC appear in no feed we carry.

How to build a CQBR Block II clone: three routes

All three end in a 10.3 inch barrel, so read the SBR rules below.

Daniel Defense Mk18 upper on your own lower

It's the fastest route. The FDE Mk18 upper group starts at $1,279.99, black at $1,299.99 and a stripped upper with the rail at $899.99. The rail is exact, but the receiver and barrel are Daniel Defense's, so both cards are equivalents.

A factory Mk18 SBR

Daniel Defense sells the MK18 as a factory SBR, so you buy it through a dealer, on a Form 4473 since October 9, 2026, or a Form 4 if you want it registered. It says the barrel matches the military upper's length and doesn't claim it was issued. FDE lists at $2,324 and black from $2,213, both equivalents.

The clone correct parts route

For the closest match, put a Colt M4CQB barrel, Mk12 block, FDE RIS II and M4QD on an LMT upper. That's about $1,180 with a gas tube at today's prices, or about $1,400 with a BCM carrier and GI charging handle. You get a Colt barrel for close to the Daniel Defense upper's price.

Mk18 RIS II builds on GPP: what they show

We counted every GunPartPicker cart holding a Daniel Defense Mk18 part from 14 January to 27 September 2026: 118 carts from 118 builders, none flagged as bots, though 50 couldn't be checked.

None is named for the Block II or Mod 1. Only 5 of those 118 carts from 14 January to 27 September 2026 pass our finished build check, partly because a complete upper has no separate barrel line, so read them as builds in progress.

What builders add around the Mk18 upper

You'll mostly find modern parts in the 118 carts created 14 January to 27 September 2026. In that window, Geissele's SSA-E X Lightning Bow trigger is in 22 of the 70 carts with a trigger. Over the same months, EOTech's HHS green kit is in 12 of 56 with an optic, and Magpul's AFG-2 in 12 of 55 with a foregrip.

The period parts builders leave out

The KAC 99051, Matech rear, SpecterDR, ATPIAL, SureFire SOCOM can and LMT SOPMOD lead no slot in these carts. Site wide from 31 January to 27 September 2026, the taupe 99051 got 3 adds and the M4QD 1, while SureFire's four prong adapter got 88 from 58 sessions.

Build cost estimate

Here's what the defining parts cost on 27 September 2026.

Builders added the FDE upper 76 times from 31 January to 27 September, and the 55 adds that carried a price had a median of $1,412. Together, the accessories cost more than the upper: about $1,160 for an EXPS3-0 and G33, about $270 for an M640U and $1,169 for a SOCOM556-RC2.

The civilian legal path to a CQBR Block II clone

SBR or pistol

A 10.3 inch barrel on a stocked lower is a short barreled rifle under the NFA. Since October 9, 2026, ATF no longer enforces the Form 1 or Form 4 approval for SBRs, so filing is optional, though worth it if your state only allows registered SBRs. Pistol builds are a different category and brace rules have shifted in court, so read our AR-15 pistol brace guide first.

Why pin and weld does not work at 10.3 inches

Reaching 16 inches would take about 5.7 inches of permanently attached device. That's impractical, and it wrecks the silhouette you're after.

Semi auto fire control parts only

Issued M4A1 lowers are machine guns, and post 1986 machine guns can't be transferred to civilians. You can't use an auto sear or any automatic parts, and we don't card the select fire Geissele listings.

Suppressors, IR lasers and state law

Since October 9, 2026 a suppressor needs no federal approval, and our guide to what changed for suppressors in 2026 covers the process. Military IR lasers aren't sold to civilians. Some states ban SBRs or suppressors whatever federal law allows.

What the internet gets wrong about the CQBR Block II

A few of these sat in our own earlier version.

The Geissele SSA was never the issued trigger

Our earlier version put the SSA in the SOPMOD Block II kit. The Geissele reported in SOCOM use by 2011 was the select fire SSF, so the semi auto SSA and SSA-E are only ever civilian stand ins.

FDE, not black, is the documented rail finish

Our old FAQ called black correct. FDE is the RIS II finish the 2009 notice names, owner charts give and the 2011 NSW rifle wears, and black is MARSOC's. No page we checked confirms the color of 01-004-16120, the part the Mk18 stock record cites.

The RIS II arrived in 2006, not 2009

Contracts went out in March 2005, the rail served from May 2006 and the Mk18 rail had a stock number by February 2007. The 2009 notice was for a follow on contract. Nothing supports the claim that Block II replaced Block I by 2012.

The CQBR Block II light was an Insight, not a SureFire

Our earlier version named the SureFire M600. The Block II light was Insight's SU-233, then the WMX200, and we found no primary source listing a SureFire as a Block II item.

SOCOM556-RC2 was never the issued can

The period cans are the KAC QDSS-NT4 and SureFire's FA556-212-DE. SureFire markets the RC2 as a second generation SOCOM series can, and the RC4 we used to card is later still.

No source ties the Block II to Neptune Spear

Our earlier version said DEVGRU may have carried Block II uppers on the 2011 raid. We found no source, so it's gone.

What our earlier version of this guide got wrong

Beyond those, the first version also got these wrong.

Block I vs Block II: which should you build?

The rail, the front sight and the optics era decide it. Our old claim that Block II shoots measurably better had no source, so don't choose on accuracy.

Pick your 10.3 inch clone: Block I, Block II or Mod 0

If a film brought you here, the Act of Valor Mk18 era carbine and the film inspired Sicario task force build are the screen versions of a short carbine.

Sources and photo credits

We cross checked every part against one enthusiast parts list, as a checklist and never as proof. Builder figures are GunPartPicker carts and adds read on 27 September 2026.

Photo credits