M110K1 clone build: KAC's 16 inch M110 carbine, part by part

In April 2011 the Army asked for a shorter, lighter M110. Knight's Armament answered with a 16 inch carbine, the M110C, and renamed it the M110K1 by the end of 2013. SOCOM bought it as a conversion kit, and by 2018, 150 had been fielded through MARSOC.

You can build a close M110K1 clone, but three parts fight you: the URX 3.1 rail, a 1 in 11 chrome barrel and an SR-25 lower. We'll show you what we stock and what you'll have to hunt.

What an M110K1 clone copies

An M110K1 clone copies KAC's 16 inch 7.62 carbine: a tan SR-25 upper, URX 3.1 rail, chrome barrel, folding micro sights and an FDE Magpul ACS on an M110 lower.

M110K1 specs from KAC's own spec card

KAC's spec card, P/N 25989-1, is dated March 2012 and appears on both its M110C and M110K1 pages. Remember its 1 in 11 twist when you shop, because most aftermarket 16 inch .308 barrels are 1 in 10.

A conversion kit for M110 lowers, not a new rifle

Crane bought M110K1 conversion kits, and the 2020 stock number records for the 6.5 CM kits say they modify M110 7.62mm weapons. So an issued K1 is a unit's own M110 lower with a carbine upper and collapsible stock. SOCOM's URG-I works the same way, as the M4A1 URGI clone build shows.

No 7.62 kit parts list has surfaced.

M110K1 vs M110 SASS and the other M110 names

Search for the K1 and you'll hit the 20 inch M110, HK's M110A1 and a 6.5 Creedmoor story. Here's what the K1 shares with each.

For 5.56 marksman clones, see the Mk12 Mod 0 SPR and the Army's 5.56 SDM-R. For 7.62 on another platform, try the SCAR-H based Mk17 Mod 0.

The 20 inch M110 SASS it converts

The M110 has a 20 inch barrel, a rifle length URX II rail, a fixed A2 profile stock and KAC's 25877 flash hider, and the K1 kit replaces all four. We list the rest in the 20 inch M110 SASS every K1 started as.

An Italian Special Forces sniper lowers a fixed stock M110 SASS to a U.S. Army Green Beret at the ISTC Urban Sniper Course, Hohenfels, Germany, 2 June 2021. U.S. Army photo by Sgt. Patrik Orcutt, public domain, via Wikimedia Commons.

KAC catalog names are not SOCOM designations

HK's M110A1, a G28 derivative, won the Army's compact sniper program in April 2016. KAC's catalog and SSD imply the 6.5 kits became the M110A3 and M110K7, but no government document we found uses either name. Our M110 SASS clone build covers both.

M110K1 history: from the M110C to MARSOC

Almost everything known about the K1 comes from KAC's pages and Crane's contract paperwork.

The 2011 Army request that produced the M110C

Kit Up! reported the Army's April 2011 wish list: a collapsible stock, a shorter barrel, 45 degree offset irons, a brake that works with a suppressor and under 9.0 lb. KAC's M110C was public by July, and its spec card says 8.97 lb.

Renamed M110K1 by the end of 2013

KAC's military listing showed the M-110C in October 2012 and the M-110K1 by December 2013, with the same description. Its K1 photos carry April 2013 edit dates, so the rename likely came earlier that year.

Who fielded it: MARSOC, SOCOM and select Navy users

Crane's justification for its 2018 contract says 150 M110K1s had been fielded through MARSOC, and that the items are used by "select members of the US Navy and SOCOM". HQ USSOCOM funded every order on that contract but one, from Navy Expeditionary Combat Command Pacific.

Marine Raiders fire the full length M110, not the K1, in Jacksonville, North Carolina, 1 October 2021. U.S. Marine Corps photo by Cpl. Brennan Priest, public domain, via DVIDS.

Our hero photo, from June 2021, shows an Army Special Forces sniper with the K1 setup, though its caption never says K1. We found nothing that confirms Rangers or NSW.

The 2018 Crane contract for conversion kits

Crane sought sources in October 2016 for K1 conversion kits, suppressors, spares and engineering services. On 2 February 2018 it gave KAC a five year IDIQ, N00164-18-D-JN50, with a $5 million ceiling. Earlier kits came through KAC's contract for the Mk11 Mod 0, SOCOM's earlier SR-25, among other buys.

M110K1 variants: 6.5 Creedmoor and the later K models

We clone the 7.62 K1 here, but its 6.5 Creedmoor offshoot and KAC's later K models get mixed up with it.

The 22 and 14.5 inch 6.5 Creedmoor kits of 2020

Crane priced a 6.5 CM upper against the 7.62 kit in October 2019 and ordered about $4.49 million of 6.5 CM kits in June 2020. Stock number records list 22 and 14.5 inch kits with a QDC brake, a carbine stock kit and a coyote brown B5 Systems precision stock. They never say M110K1, so that link is inferred.

The B5 is the kit's stock, though the records don't say which cheek riser length. KAC's K7 and SR-25 Precision uppers are 6.5 CM equivalents, and only the Precision was in stock on 27 September.

Later KAC K models and SOCOM's 2023 Geissele award

KAC has since listed the K2, K3, K5, K6, K7, A2 and A3. The M110K3 is 16 inch and 1 in 10, and KAC lists the M110K7 at 14.5 inches in 6.5 CM. SSD photographed a 6.5 CM K7 at AUSA 2021, captioned as the version USASOC uses.

SOCOM signed an MRGG-S sniper IDIQ with Geissele on 29 September 2023, and no source we found says it replaces the K1.

M110K1 parts list: the issued part and what to buy

Here's every slot, with its evidence and what you can buy from us. We cross checked NS Armory's clone recipe, the only real steel K1 list we found.

Parts from this guide that we stock. Product photography is supplied by the listed merchants through their affiliate feeds.

Exact is the same part or its current version, equivalent a different product doing the job, budget a cheaper stand in, hunt used only and unobtainable military only.

The lower receiver group

On an issued K1 these stayed with the unit's M110, but you'll buy every one.

Lower receiver: the host M110, or a KAC SR-25 lower

Issued kits went on government owned M110 lowers roll marked RIFLE 7.62 MM M110. No kit document names the lower, but the K1 name, KAC's 2013 photo and the 2021 Army photo all point to it.

KAC's SR-25 lower is your equivalent, and it was out of stock on 27 September. Any other lower has to be SR-25 pattern.

Trigger, controls and guard: kept from the host M110

KAC lists ambidextrous controls, and those live in the lower. No document names a K1 trigger or guard, and KAC's 2013 photo shows a flared guard nobody has identified.

All four cards are AR-15 stand ins with no stated SR-25 fit, so ask your lower's maker first.

Stock: FDE Magpul ACS, buffer part number unconfirmed

KAC's text says 10 position sliding stock, but every photo we found shows an FDE Magpul ACS, so use one. NS Armory's "M110K1 buffer" link goes to KAC KM21057, an SR-15 and SR-16 buffer by its own page, so the right buffer is unconfirmed.

The ACS was out of stock everywhere we matched on 27 September, so the STR is your fallback. Luth-AR's AR-10 tube assembly isn't confirmed in a KAC lower.

Grip: FDE Magpul MOE, or a MIAD

KAC's photos show an FDE Magpul MOE, and NS Armory's recipe uses an FDE MIAD.

The upper receiver group

The kit's upper assembly covers this group, though nobody published its exact contents. KAC sold the SR-25 ECC as the K1's commercial counterpart.

Upper receiver: tan SR-25 flat top from the kit

The kit upper is a tan KAC SR-25 flat top. KAC's SR-25 K3 16 inch upper is the closest you can order, with a later rail and a 1 in 10 barrel, and it was out of stock on 27 September. We don't list a stripped SR-25 upper yet.

Barrel: 16 inch chrome plated, 1 in 11 twist, dimpled

KAC never published the profile, though one 2023 AR15.COM reply says the K1 barrel tapers, unlike the M110's. We don't list a 1 in 11 or dimpled 16 inch barrel, so the Criterion is an equivalent and the Faxon is the budget pick.

Criterion's rifle length barrel is 1 in 10, and our feed data for the Faxon doesn't settle its twist. Neither says SR-25, so confirm fit.

In 2014, AR15.COM clone builders cut 20 inch .308 barrels to 16 inches and had them dimpled.

Gas block: low profile, rifle length tube on clones

KAC never published the gas length, but its URX 3.1 rail text recommends rifle length gas to avoid block interference. NS Armory pairs a machined K1 block with KAC's KM20173 pin and a rifle length tube, and we don't list that block or the pin.

Treat all three as stand ins and match the block to your barrel's gas journal. One 2014 AR15.COM builder warns that Armalite length tubes run slightly longer than KAC's rifle length.

Muzzle device: the MAMS brake and QDC stand ins

KAC's text says MAMS brake, and its photos show a perforated brake on a QDC collar. The ECC used KAC's 762QDC flash suppressor, and NS Armory's recipe uses KAC's five slot 7.62 QDC flash hider. Which 7.62 MAMS the K1 used, and its barrel thread, aren't documented.

The open brake is an equivalent, and KAC makes it in 3/4x24 and 5/8x24, so match your barrel.

KAC's QDC MAMS kits in .30 caliber carry the name KAC's text uses: 30598 in 5/8x24 and 30169 in 3/4x24. Neither was in stock on 27 September, and which one fits a K1 barrel isn't documented.

Bolt carrier group and charging handle: SR-25 pattern

KAC names the Carbon Cutter carrier. Nobody documented the handle, and SR-25 handles don't fit every AR-10, so see our guide to SR-25 pattern charging handles.

Radian's handle is an equivalent. Faxon's carrier is a budget pick nobody has confirmed in a KAC upper, and KAC's SR-25 E2 Mod 1 carrier, 31476, sits in two feeds we haven't matched.

The URX 3.1 rail, micro sights and optic

The rail defines the K1, and it's the hardest part to find.

Handguard: KAC URX 3.1 7.62, 13.5 inch, P/N 30259

KAC's text says URX III, and sellers identify the URX 3.1 7.62, P/N 30259: short 1913 sections at each end, slick sides, a removable bottom rail, four QD sockets and no M-LOK slots. The 2021 Army photo shows that marking on an M110, one digit blurred.

NS Armory says it fits the SR-25 only and needs KAC's KM23383 wrench. No feed carries it, and the only URX 3.1 we list is the AR-15 version, the wrong platform. You'll have to hunt one used.

The Sons of Liberty rail is an M-LOK equivalent sold as fitting the SR-25. The BCM swivel is a push button QD for the sockets.

Iron sights: KAC folding micro, inline or offset

KAC's text says 45 degree offset micro sights, but its own K1 photo and the 2019 SOCOM image show them inline, so which was issued is disputed. We'd follow the photos.

KAC's folding micro sights are the exact parts. The micro front was out of stock on 27 September, so Troy's micro set is the in stock equivalent.

Optic and scope mount: Leupold in photos, none on record

The optic wasn't part of the kit, and no record names one. KAC's photos show Leupold scopes in a KAC one piece mount, so treat these as style picks. KAC's taupe one piece mount sits out of stock in one merchant feed, and we don't carry it yet.

Suppressor, magazines and the taupe finish

Three items finish it, and only the can is an NFA item.

Suppressor: a KAC QDC can, model never named

Crane bought "sound suppressors" for the K1 without naming a model. The 6.5 kits call for a QD CRS PRT 7.62 in FDE, P/N 114569-FDE, a military part number we can't match to the retail CRS-1.

Both are equivalents and NFA items.

Magazines: PMAG 20 LR and KAC steel 20 rounders

The 2021 Army photo shows a PMAG 20 LR, and KAC's photos show steel 20 rounders. KAC's SR-25 steel 20 round magazine matches its photos, and it was out of stock on 27 September. Magpul's PMAG 20 LR/SR Gen M3 is the current version of the one in the Army photo.

Finish: KAC tan, and the taupe Cerakote split

KAC calls it terrain matching tan. NS Armory does taupe Cerakote on the receivers, rail and small parts and black on the gas block and forward barrel, but that's one shop's recipe.

A 2013 AR15.COM poster, judging from KAC's photos, said its tan looked very different from Magpul FDE.

What you can buy today and what is unobtainable

We checked every part against our feeds on 27 September 2026, and the cards show live prices.

M110K1 parts in stock on GPP today

In stock: the FDE grips, KAC's micro rear sight, QDC brake, flash suppressor and CRS-1, the Radian handle, the B5 stock, the PMAG and the barrels. The ACS, KAC's front sight, the MAMS kits, KAC's magazine, the SR-25 lower and the K3 upper weren't.

Parts to hunt used, and the military only kit

You'll hunt the URX 3.1 7.62 and a 1 in 11 barrel, and wait on KAC's MAMS kits to come back in stock. The kit upper, issued M110 lowers and the FDE kit part numbers are military items nobody can sell you.

What an M110K1 clone costs today

Here's the closest in stock part for each slot on 27 September 2026.

That total can't build a rifle. It lacks a lower, an upper, the URX 3.1 and a front sight. When builders added KAC's SR-25 lower to carts from 31 January to 27 September 2026, the median price was $1,528.31 across 43 priced adds.

The Leupold 1 to 4.5x adds $879.99 and the CRS-1 $1,353.75. NS Armory listed its K1 conversion service at $2,000.00 on 27 September, with the parts it needs listed separately.

How to build an M110K1 clone: ECC, K3 or parts

Three routes get you close, and none gets you all the way.

SR-25 ECC: the discontinued civilian twin

KAC's 2012 SR-25 ECC, P/N 30313, had a 16 inch chrome lined 1 in 11 barrel, the URX 3.1 and a 762QDC flash suppressor. It's discontinued, so you'll buy one used. KAC's ECC text never mentions dimples, and one 2022 AR15.COM reply calls the K1 an ECC in taupe.

SR-25 K3: the closest new KAC rifle

KAC's SR-25 K3, P/N 121475, is 16 inch and 8.7 lb with a 1 in 10, dimpled 416R barrel and a later URX rail. It's a K1 successor and an equivalent at best, out of stock on 27 September.

A parts clone on SR-25 pattern receivers

Use KAC receivers or clones that take KAC barrel and rail parts, since DPMS pattern parts won't interchange. Here's why AR-15 and AR-10 parts do not cross over. Then work down the parts list above.

What GPP builders pair with a 16 inch KAC upper

Nobody on GPP named a build after the M110K1 from 10 December 2025 to 27 September 2026. We found 24 carts, created 30 January to 25 September 2026, holding a 14.5 or 16 inch KAC SR-25 upper.

From January to September 2026, only 5 pair it with KAC's SR-25 lower, and just 2 of those hold a 16 inch upper. At least 5 of those January to September carts put it on an AR-15 lower, which can't work. None has the K1's FDE ACS, micro sights, URX 3.1 or QDC brake, so nobody here has assembled the K1 look yet.

What the internet gets wrong about the M110K1

Most errors trace to Wikipedia or 2019 news stories.

The K1 is the 7.62 carbine, not the 6.5 kit

Wikipedia treats the K1 as the 6.5 CM kit ordered in October 2019. Crane bought 7.62 kits before and after February 2018, and the 6.5 CM order came on 19 June 2020.

No Army adoption, and MARSOC is not the whole Corps

Defence Blog said in October 2019 that the Army and Marine Corps had recently adopted the K1. The Army's compact rifle became HK's M110A1, and the Marine K1s went through MARSOC, as VFC's airsoft marketing says. We found no Navy designated marksman program either, despite a Wikipedia list calling it one.

The 2019 photo shows a URX 3.1, not M-LOK

National Interest said 2019 photos showed the K1 had traded its quad rail for M-LOK, and reposts repeated it. The image was a SOCOM brief placeholder of the K1 upper kit, and its rail is a URX 3.1. An SSD commenter says the 6.5 CM selection uses M-LOK, which we couldn't verify.

Airsoft parts lists are not real steel lists

The top "M110K1 parts list" result in our search check was VFC's airsoft parts PDF, followed by RedWolf and 3D print files. Those fit replicas, so use our table for real steel.

The civilian legal path to an M110K1 clone

The K1 is already semi automatic with a 16 inch barrel, so it's an easy clone to keep legal.

Semi auto and 16 inches: no SBR paperwork

The issued K1 is semi automatic, so you won't swap any auto sear parts. A 16 inch barrel makes it a Title I rifle if overall length with the stock collapsed stays at 26 inches or more, and KAC's K3 is 34.5 inches collapsed.

Copying the 14.5 inch 6.5 kit: SBR or pin and weld

A 14.5 inch upper, from the 6.5 kit or KAC's K5 and K7, makes an SBR on a rifle lower. Pin and weld a device to reach 16 inches, or check your state's SBR rules first. ATF announced on October 9, 2026 that it would stop enforcing SBR approval and registration.

The QDC suppressor, NFA transfer and state law

KAC's QDC and CRS cans are NFA items, but ATF announced on October 9, 2026 that it would stop enforcing approval and registration for suppressors. Our guide to suppressor paperwork after the tax change covers the tax and the forms. Some states restrict suppressors, SBRs, pistol grips, collapsible stocks or magazine capacity. Check yours before you buy.

Sources and photo credits

We credit NS Armory's recipe where we use it.

Reference photos: what each one really shows

Our hero shows an Army Special Forces sniper in June 2021 with an M110 lower, URX 3.1, FDE ACS and PMAG 20 LR. That's the K1 setup, though the caption never says K1, and the barrel sits out of frame. KAC's K1 photo and M110C photo are KAC copyright, so we link them, along with the 2019 SOCOM image.