M4A1 URGI Clone Build Guide: The Modern SOCOM Standard

In March 2018 the federal supply catalog gave a stock number to a box of parts: NSN 1005-01-671-3911, the 14.5 inch Upper Receiver Group, Improved. Fit it to a SOCOM M4A1 and the carbine keeps its lower, receiver and bolt carrier. The barrel, gas system, rail and charging handle change.

So a URGI clone is mostly an upper build. We matched every kit part to its catalog record and priced what you can buy today.

The M4A1 URGI setup at a glance

The kit's catalog record lists seven lines. The Daniel Defense barrel (07-077-07308) arrives with its pinned gas block. The other six are a mid length gas tube, its pin spring, Geissele's Airborne charging handle (05-664S) and Mk16 13.5 inch handguard (05-650S), three Magpul MAG582 rail sections and a MAG606 QD sling mount.

The kit holds no muzzle device, sights, upper receiver or bolt carrier. You supply those, plus a semi auto lower.

What is the URGI?

URGI stands for Upper Receiver Group, Improved, and the federal catalog spells it URG-I. It's a modification package for the M4A1s that Army Special Operations Command units already carried with the SOPMOD Block II kit.

Units keep the lower, receiver and bolt carrier, so the rifle stays an M4A1, and in Block program terms a Block II weapon.

The kit replaced the Block II upper's heavier SOCOM profile carbine gas barrel and its Daniel Defense RIS II quad rail.

Why the URGI exists

NSWC Crane, the Navy center that manages SOF small arms, laid the groundwork. In May 2018 it briefed industry on 14.5 inch cold hammer forged M4A1 barrels with mid length gas, tested for USASOC.

Crane's 14.5 inch mid length test

Crane set the gas block about 9.8 inches from the bolt face with a .076 inch port and ran H2 buffers. Three carbines fired 30,400 rounds of M855A1, and accuracy hadn't changed at 12,600. SOF M4A1 barrels usually start to degrade around 6,000. The report doesn't name the barrel maker.

What the Mk16 saves over the RIS II

Less than you've read. Geissele lists the 13.5 inch Mk16 at 14.9 oz with its barrel nut, and Daniel Defense lists the discontinued M4A1 RIS II at 17.7 oz without saying if that counts its nut.

The AR15.COM reference thread weighed whole uppers with the same muzzle device: 1.89 kg for a 14.5 inch URG-I, 2.00 kg for a RIS II upper on a government profile barrel. Our earlier version said 11 oz. It was wrong.

Who carries the URGI

USASOC owns the program, and use spread over years. Our title calls the URGI the modern SOCOM standard. That holds today in a loose sense: The Firearm Blog wrote in May 2026 that it sits on most SOCOM M4A1 lowers, and Crane already wants to replace or upgrade it.

Army Special Forces groups

Military Times reported in October 2018 that the URG-I was being phased into the Special Forces groups and the 75th Ranger Regiment, with a barrel designed around M855A1.

The earliest public photo we found, from 14 October 2019, shows a 3rd Special Forces Group soldier firing an M4A1 with a DDC Mk16 and an Airborne charging handle. You can see it on Wikimedia Commons. Photos of 10th Group carbines from August 2026 show tan Mk16 style rails on barrels you can't measure.

A 1st Battalion, 10th Special Forces Group (Airborne) Green Beret confirms zero with a suppressed M4 pattern carbine and a tan Mk16 style handguard, Baumholder, Germany, 20 August 2026. Its barrel length can't be judged, so it may or may not be a URGI. U.S. Army photo by Daryl Averill Jr., public domain, via Wikimedia Commons.

75th Ranger Regiment

The Rangers are named in the 2018 reporting, but we found no open source photo of a Ranger URGI.

Marine Raiders and the MARSOC kit

The catalog settles this one. NSN 1005-01-684-1906, assigned 24 October 2019, is titled "URG-I 11.5 MARSOC": an 11.5 inch kit with no flash hider. The AR15.COM thread calls the same NSN a USASOC kit, so whether a separate USASOC 11.5 exists is still open.

Naval Special Warfare

Only the AR15.COM reference thread describes an NSW configuration (see the variants below), and we found no official record of one.

URGI variants over its service life

Every date here comes from a federal catalog record or a Navy contract notice unless the timeline marks it otherwise.

The 14.5 inch kit (2018)

NSN 1005-01-671-3911 was assigned on 26 March 2018. Its part number sources are Atlantic Diving Supply ("14.5 URGI-KIT"), Daniel Defense and Navy CAGE 12255, the code for NSWC Crane.

The 11.5 inch URGI (2019)

The 11.5 inch version first shows up as the 2019 MARSOC kit. The thread gives its parts: DD's 11.5 inch government profile carbine barrel (07-077-07108, a number DD's site confirms), a 10.5 inch Mk16 in DDC (05-1073S) and DD's carbine gas tube (04-013-01009). We can't match that tube to a listing yet.

A flash hider can't practically take 11.5 inches to 16, so the rifle is an SBR, and the legal section covers what that means now. The 10.5 inch DDC rail is out of stock everywhere.

Serialized complete uppers (2021)

On 8 February 2021 the catalog added serialized 14.5 inch (NSN 1005-01-693-3608) and 11.5 inch (NSN 1005-01-693-3616) complete uppers with Crane part numbers. They're cataloged as receivers, so they most likely include one, though no record says so.

Crane also awarded Daniel Defense a barrel contract (N0016422DJN02) in March 2022, with a 9.1 million dollar ceiling through March 2027.

The URG-IG grenade launcher upper (2023)

Cataloged on 31 March 2023 (NSN 1005-01-708-3468), the URG-IG is a serialized 14.5 inch upper modified to take the M320 grenade launcher module on a quick disconnect mount. The M320 is a 40mm launcher, so it's no clone part, and we found no public photo of the mount.

The NSW URGI configuration

Per the AR15.COM thread alone, the NSW version runs two MAG582 sections, a Magpul MAG631 tape switch plate, two sets of Geissele DDC rail panels (04-428S) and a MAG607 Paraclip.

HICAR and the next upper (2026)

In May 2026 Crane opened HICAR (N0016426SCA004), seeking a carbine that beats the current URG-I and fits the M4A1 lower with no permanent modification. Soldier Systems Daily reported an 11 to 12 inch barrel and a 300 to 600 m goal.

Daniel Defense is also taking a new rifle to military trials. Here's what we know about the DD4 X1.

The complete parts list

Here's the M4A1 URGI parts list, slot by slot. We cross checked every row of one enthusiast parts list against the catalog records, and we flag where we disagree.

Twelve in stock parts carded in this guide, laid out overhead: the kit's barrel, rail, charging handle and rail section, then host rifle parts and civilian stand ins. Product photography is supplied by the listed merchants through their affiliate feeds.

The URGI kit: barrel, gas system and rail

Your clone has to get these right, and the catalog record documents each one.

Barrel: Daniel Defense 14.5 inch mid length

DD P/N 07-077-07308 is a 14.5 inch cold hammer forged, chrome lined barrel with a 1:7 twist, government profile, mid length gas and a low profile gas block. DD doesn't publish a port size, so the .076 inch figure comes from the thread, Crane's briefing and Geissele's listing.

Talk that the issued barrel's steel differs traces to one secondhand 2018 forum post and is unconfirmed.

Card one is the issued part, with one offer today. Card two is a DD equivalent, the same barrel without its block.

Gas block: Daniel Defense pinned low profile

The kit record describes a tapered pin block installed on that barrel, so buying the barrel gets you the block. A 2018 forum list named a "DD MK12 gas block", and the enthusiast list calls the Mk12 "originally spec'd", but DD's retail Mk12 uses set screws. The record rules out a set screw block, not a pinned one shaped like the Mk12.

Both cards, DD's set screw Mk12 and Geissele's Super Gas Block, are equivalents.

Gas tube: Daniel Defense mid length

The kit record lists P/N 04-013-09401, and no DD retail SKU matches it. The thread gives 04-013-18034, DD's current retail mid length tube. Buy that one. We list it, but no merchant has it in stock today, so BCM and CMMG tubes are the in stock equivalents.

Handguard: Geissele Mk16 13.5 inch DDC

Geissele P/N 05-650S is NSN 1005-01-672-4797, cataloged in "COLOR SAND" with the 14.5 kit as its next higher assembly, and Geissele's own page says USASOC adopted it. Its set screw (06-102) has its own NSN, 5305-01-672-4796, and we don't stock it.

The first card is the issued rail. The black Mk16 card is an equivalent, the same rail for about $68 less in the wrong color.

Charging handle: Geissele Airborne DDC

Geissele P/N 05-664S is NSN 1005-01-672-4803, "CHARGING HANDLE M4, SAND COLOR", used on the 14.5 inch, 11.5 inch and URG-IG uppers. The second card is Geissele's commercial DDC Airborne, an equivalent without the subdued URG-I markings.

M-LOK rail sections: three Magpul MAG582

The kit and all three serialized upper records carry three Magpul MAG582 7 slot aluminum sections, and the enthusiast list leaves them off. Buy three.

Front sling mount: Magpul M-LOK QD

The kit's last line is one Magpul MAG606 M-LOK QD sling mount.

Upper parts kept from the host rifle

Issued rifles kept their own. On a clone, you pick these.

Upper receiver: Colt M4A1 flat top

The kit reuses the unit's existing M4/M4A1 upper, so Wikipedia's claim that URG-I uppers are built by Colt doesn't fit the kit, and no record names who made the receivers on the 2021 serialized uppers. A long time AR15.COM poster calls both Colt C stamp and CAGE code uppers correct. The enthusiast list adds a Mueller upper we couldn't verify.

The Colt upper card is out of stock today, and the T marked Expo Arms and Wilson Combat forged uppers are budget stand ins.

Bolt carrier group: Colt, FN or contract

Issued rifles kept a standard M16/M4 carrier, and no record names a maker, so any standard M16 profile carrier matches. BCM's carrier is in stock, Colt's isn't, and we don't stock an FN carrier. Geissele's REBCG ships only on its near clone, so it's an equivalent.

Muzzle device: SureFire 4 prong, model disputed

Neither kit record includes a flash hider. The maintained AR15.COM list names the SureFire FH556RC. A January 2018 list, called correct by a user claiming program knowledge, names the SF4P, and the 2019 photo can't tell them apart.

We don't stock the SF4P. The SF3P card, from Geissele's 2018 civilian upper, is an equivalent.

Suppressor: SureFire SOCOM RC

The AR15.COM list gives a SureFire SOCOM556-RC in Dark Earth, and the same 2018 insider called it the legacy SOCOM556-RC. No feed we carry has it. Both cards are equivalents, and both are NFA items.

The lower receiver group

The URGI never touches the lower. Issued lowers are select fire, and those parts are machine gun parts, so your clone takes semi auto parts.

Lower receiver: Colt A2 profile, semi auto for civilians

The enthusiast list gives a Colt A2 profile lower with a UID label. You need a semi auto M4 lower, and we don't stock a Colt one alone yet. The Colt carbine card is an equivalent, a Colt marked lower if you use it as a donor. PSA's "M4 CARBINE" lower is the budget route, and Aero's clone lower is out of stock.

Trigger: Geissele SSF issued, SSA for civilians

The thread gives the Geissele SSF (05-102), which Geissele says Crane safety certified. The SSF is a machine gun part, so we don't card it. Both cards are semi auto equivalents: the SSA the enthusiast list names and CMMG's standard trigger kit.

Safety selector: Colt ambidextrous

The thread alone lists a Colt full auto ambi selector, P/N SP401017. You need a semi auto ambi. We haven't found a semi auto Colt one, so CMMG's is the budget stand in.

Buffer and spring: carbine spring with H2 buffer

The thread gives a standard receiver extension, carbine spring and H2 buffer, and Crane's test carbines ran H2 buffers. The Geissele Super 42 and H1 card is the near clone setup, an equivalent.

Stock: SOPMOD, Magpul or Colt CAR

Stocks varied. The thread lists Type I, IIA, IIB and Gen 1 SOPMOD, and the enthusiast list adds the Colt CAR and Magpul CTR. The 2019 photo shows a black Magpul stock in the MOE SL style. We don't stock a Colt CAR stock right now, and the B5 SOPMOD Bravo is a budget SOPMOD look.

Grip: A2, Ergo or Magpul MIAD

The thread gives a standard A2 grip, and the enthusiast list adds Ergo and MIAD. The Ergo card is our guess at the model.

Trigger guard: GI

The enthusiast list says GI, with no source we could check.

Rear sling mount: CQD

This row comes only from the enthusiast list too. We don't stock a CQD mount, so both cards are functional stand ins, not look alikes.

Sights, optics, lights and lasers

None of these are kit parts, and they varied by user and year.

Rear sight: MaTech flip up

The thread credits the MaTech flip up to the Army supply system. A long time poster says KAC 300 m and 600 m sights are issue too, and that units bought ARMS #40 and #40L sights off the shelf. Magpul offsets turn up as well, and we don't card those. Only the MaTech deployable is in stock today, and the MBUS Pro is a budget stand in.

Front sight: KAC folding, taupe or black

Owner consensus says a KAC folding front in taupe, P/N 99051, and the enthusiast list allows black. None is in stock today, so the Magpul MBUS Pro is the budget stand in.

Optic: S-VPS scopes, EOTech or Aimpoint

No single optic belongs to the URGI. SOCOM's Squad Variable Power Scope awards of 28 September 2018 went to the Nightforce ATACR 1-8x and a SIG scope that trade press called the TANGO6 1-6x24.

Military photos add an Aimpoint Micro type dot in 2019, and an Aimpoint on a Unity mount and an EOTech in 2026.

A 10th Special Forces Group Green Beret adjusts an Aimpoint type red dot on a carbine with a tan Mk16 style handguard, laser and weapon light, Baumholder, Germany, 20 August 2026. U.S. Army photo by Daryl Averill Jr., public domain, via Wikimedia Commons.

The enthusiast list adds a Vortex Razor 1-6, Kahles K16i, Nightforce NX8, EOTech 553, Elcan SpecterDR and Aimpoint CompM4s, which we haven't carded. Our ATACR card is the commercial F1 without the contract's SOCOM reticle.

For the dots in the photos:

Light: SureFire Scout or Insight WMX200

A thread poster wrote in March 2023 that the Insight WMX200 was the older issue light and SureFire M640V Scouts were being issued. We don't stock the WMX200, or the M3X and X400V that the enthusiast list adds. The M640U card is a cheaper white light Scout.

Laser: PEQ-15, LA-5 and civilian swaps

The enthusiast list gives the PEQ-15, its commercial ATPIAL-C and the LA-5. Issue power IR lasers aren't sold to civilians, so every card here is a civilian equivalent, and the ATPIAL-C card has no offers today.

Foregrip: Magpul AFG or RVG

The enthusiast list gives a Magpul AFG or RVG with no source. The RVG is Picatinny, so it goes on one of your MAG582 sections.

Magazine: 30 round Magpul PMAG

Standard 30 round magazines. The 2019 photo shows a black Magpul PMAG with Gen M3 style markings, and the black Gen M3 is the one to buy.

What you can buy today and what is unobtainable

We counted one row per role for a 14.5 inch USASOC build, 26 roles, against our catalog on 27 September 2026.

Clone correct URGI parts in stock on GPP today

Every kit line but the gas tube and its pin spring is in stock: the DD barrel (one offer), the Mk16 (seven), the Airborne (eight), the MAG582 (nine) and the MAG606 (ten). So are the FH556RC, H2 buffer parts, a MaTech rear, both S-VPS scopes and the M640V.

Close substitutes

Semi auto lower parts for the select fire ones, an RC2 for the legacy RC, a civilian laser for the PEQ-15, and a BCM or CMMG tube until DD's is back in stock.

Parts no retailer can sell you

The select fire lower and its parts, issue power PEQ-15, LA-5 and NGAL lasers, the M320 and its mount, and the kit's own gas tube and pin spring numbers. The legacy SOCOM556-RC, the WMX200 and the Mk16 set screw aren't in any feed we carry.

How to build a URGI clone: three routes

You have three routes, and each trades accuracy against money and paperwork.

The Geissele URGI near clone upper

Geissele's URG-I near clone (SKU 08-159) is the one box route. It shares the Mk16 and Airborne with the kit, and the table shows where it doesn't.

Geissele listed it at $1,525, out of stock, when we checked. Five merchants in our catalog have it from $1,382.99. Its 2018 predecessor sat closer to issue, with a DD barrel, a pinned block and a standard M4 carrier.

Both cards are equivalents, and the 11.5 inch 08-315 is out of stock and makes an SBR. We skip Geissele's 10.3 inch 08-176, since no 10.3 inch URGI is on record.

The clone correct parts route

Put the kit's own part numbers on a standard M4 upper with a standard M16 carrier, a taupe KAC front, a MaTech rear and your pick of muzzle device. Every part has a card above. You'll pay more than the near clone, and the removable FH556RC leaves the 16 inch problem open.

The practical URGI

Keep what defines the look, the Mk16, the Airborne and a mid length government profile barrel, and choose the rest for how you shoot. DD's 16 inch government mid length barrel keeps it a rifle, so state SBR rules never apply, and a black Mk16 saves about $68. Our AR-15 barrel length guide covers what you trade between 14.5 and 16 inches.

URGI builds on GPP: what they show

Only one GPP cart created from December 2025 to 27 September 2026 carries this rifle's name, and it holds two parts, so we counted by part. We took carts created 1 January to 27 September 2026 that hold a Geissele URG-I upper or a Mk16 13.5 rail, minus seed carts, carts under five parts and bot owned carts.

That left 115 carts from 114 owners over those dates, median 11 parts. They're carts in progress, not finished rifles.

The 23 who built on the Mk16 rail from 1 January to 27 September 2026 mostly copied the kit's geometry and skipped its brands. In those carts, 15 of 21 barrels were 14.5 inches, and 15 of 16 gas tubes were mid length. Yet in the same carts only 4 were the DD government barrel, and 3 of 20 charging handles were the Airborne.

What builders add around the upper

The rest lean Geissele and coyote. In the 115 carts created 1 January to 27 September 2026, the SSA-E X Lightning Bow fills 36 of 96 trigger slots, Geissele's DDC buffer tube 21 of 35, and B5's coyote SOPMOD leads stocks at 12 of 72. None of those are issued picks.

Across GPP from 31 January to 27 September 2026, DD's 14.5 inch mid length government barrels drew 181 adds, our strongest URGI part signal. Black Airborne handles drew 82 adds in that window, against 32 for the kit's DDC.

Build cost estimate

We priced two routes from the lowest in stock offer per part on 27 September 2026. Prices move daily.

The near clone is the cheaper upper, and it's already 16 inches. The parts built upper costs $183.64 more and still needs a pinned device, or it's an SBR.

The civilian legal path to a URGI clone

Pin and weld to reach 16 inches

The issued 14.5 inch barrel makes an SBR in civilian hands unless a permanently attached muzzle device brings it to 16 inches. Pinning and welding is the usual method, and Geissele's 08-159 does it with an SF4P.

Nobody has confirmed a pinned FH556RC gets there, so measure yours first. A pinned device also makes a QD suppressor mount harder to service.

Build it as a short barreled rifle

Or keep the removable FH556RC and build it as an SBR. An 11.5 inch clone has only this route. Since October 9, 2026, ATF no longer enforces SBR approval or registration, so federally you can assemble it today. A Form 1 is optional and costs $0, and it's the safer route if your state only allows registered SBRs. Some states ban SBRs outright, and crossing state lines with one still needs ATF approval on Form 5320.20.

Semi auto lower parts only

The issued lower, SSF and full auto selector are machine gun parts. Use a semi auto lower, trigger and ambi selector.

Suppressors, IR lasers and state law

A SureFire SOCOM can is still an NFA item, but since October 9, 2026 it needs no ATF approval, and a Form 4 is optional. For the tax and paperwork as they stand now, read what changed for suppressors in 2026.

Use a civilian legal laser, and check your state on barrel length, muzzle devices, magazines and features.

What the internet gets wrong about the URGI

Most of these trace to Wikipedia's URG-I article and to parts lists that copy each other.

Block III and Mk18 Mod 2 are nicknames

The Reptile House's 2019 primer and Wikipedia both say URGI rifles are still M4A1s and, in Block terms, Block II. Block III and Mk18 Mod 2 are nicknames. The Mk18 name belongs to the 10.3 inch CQBR line, covered in our Mk18 Mod 0 clone build.

A mixed vendor kit, not a Geissele contract

Wikipedia names Geissele as the URG-I's designer and maker. The catalog shows Daniel Defense barrel and gas parts, a Geissele rail and handle, Magpul accessories and Crane part numbers on later uppers. The barrel contract went to Daniel Defense.

No 10.3 or 13.9 inch URGI on record

Wikipedia lists a 10.3 inch URG-I with a 10.3 inch Mk16. Geissele makes the Mk16 in 9.3, 10.5, 13.5 and 15 inches, the thread says no 10.3 was issued, and the catalog shows only 14.5 and 11.5. Its 13.9 inch claim cites a dealer listing.

USAF SOF runs 10.3 inch carbines with a 9.3 inch Mk16, and The Reptile House says those aren't URG-Is. If you want a 10.3 inch clone, see our CQBR Block I clone build or CQBR Block II clone build.

REBCG, Super 42 and SSA are not kit parts

The kit holds no carrier, spring, buffer or trigger. The REBCG and Super 42 come with Geissele's near clone, while issued carbines run a standard carrier, an H2 buffer and, per the thread, the SSF.

The Mk16 NSN that keeps getting copied wrong

Retailers, The Reptile House and the AR15.COM list print 1005-01-672-4794. That NIIN is cataloged as NSN 4730-01-672-4794, a pneumatic manifold for the Stryker. The rail is 1005-01-672-4797, as Geissele's own page shows.

S-VPS scopes are Nightforce and SIG, not Vortex

S-VPS went to Nightforce and SIG in September 2018, and neither award report mentions Vortex. The Razor 1-6 is fine on your build, but nothing ties it to S-VPS.

What our earlier version of this guide got wrong

We rewrote this guide on 27 September 2026. The earlier version got these wrong.

Block II vs URGI: which should you build?

Both run on the same lower, so you're choosing an upper. The Block II's is a Daniel Defense RIS II quad rail over a heavier SOCOM profile carbine gas barrel. The URGI's is the Mk16 over a 14.5 inch government profile mid length barrel, and it weighs less (see the weights above).

Before the URGI: a 1st Battalion, 10th Special Forces Group (Airborne) soldier aims an M4A1 with a quad rail handguard in Boeblingen, Germany, 23 January 2015. The URGI kit later replaced the Block II upper's RIS II rail and carbine gas barrel. U.S. Army photo by Adam Sanders, public domain, via Wikimedia Commons.

Pick the Block II, covered in our M4A1 Block II clone build, for the quad rail years. Pick the URGI for the upper SOCOM carbines wear now, with a rail you can still buy: DD lists the RIS II as discontinued. For the earlier SOPMOD Block I carbine, see our M4A1 Block I clone build.

Sources and photo credits

Every fact above traces to one of these.