Mk12 Mod H clone build: the 16 inch Holland SPR, part by part

In July 2007, according to Small Arms Defense Journal, Precision Reflex rebuilt 12 Mk12 Mod 0 rifles at Fort Campbell, Kentucky, home of the 5th Special Forces Group. The 18 inch barrels came off. On went 16 inch Douglas barrels with mid length gas.

Collectors call the result the Mk12 Mod H.

What a Mk12 Mod H clone copies

The Mk12 Mod H is a Mk12 Mod 0 Special Purpose Rifle rebuilt around a 16 inch barrel. The Mod 0 was NSWC Crane's 18 inch precision AR, and Army Special Forces were among its main users.

Where the Holland name comes from

Collectors named it, and no issued document uses the name.

The Steve Holland account and who tells it

Forum researchers credit Master Sergeant Steve Holland, described as a 5th Group soldier, and Charlie's Custom Clones says Holland was part of the group that developed the original SPR. No official source names him. The SGM (Ret.) Daryl Holland in Wikipedia's SPR history is a different Holland.

Why the rifles may still be Mod 0 on paper

SADJ's account never says Mod H or Holland, and a 2016 poster who said he served in 5th Group never heard the setup called the Holland.

Other posters argue the rifles stayed on the books under the Mod 0's NSN, 1005-01-504-3275. We found no NSN for a Mod H.

Mk12 Mod H variants over its service life

One batch has a date and a count. The rest comes from owners reading photos.

The July 2007 Fort Campbell rebuild

Here's what SADJ lists for the 12 rifles.

Three batches, by the forum's account

The AR15.COM thread that collected the Holland story in October 2016 sorts the rifles into three batches.

For a visual clone, you'd copy the middle batch: worn paint on the receivers, a bare FDE forearm and barrel. No source maps SADJ's 12 Douglas barreled rifles onto these batches.

Mk12 Mod H vs Mod 0 and Mod 1

All three carry an OPS Inc brake and collar to mount the suppressor. The barrel, gas system and rail tell them apart.

What changed from the Mod 0

The Mod H lost two inches of barrel and went from 1:7 to 1:8 twist and from rifle length to mid length gas. SADJ lists a rail mounted front sight in place of the front sight gas block, and owners say PRI's shorter Recce rail replaced the ARMS #38 Swan sleeve. Our Mk12 Mod 0 clone build covers the 18 inch rifle.

Why the Mod H is not a 16 inch Mod 1

Primary Arms wrote in 2024 that the Mod H was a 16 inch Mod 1. The Mod 1 is defined by its KAC free float RAS, a quad rail, and the Mod H kept a round PRI forearm.

An Army Special Forces soldier sights a Mk12 in Rawah, Iraq, on 7 September 2007, two months after the Fort Campbell rebuild. The forearm is out of frame, but the same soldier's rifle shows the KAC quad rail of the Mod 1 pattern in a companion Navy photo from that day, so it's likely not a Mod H. U.S. Navy photo by Petty Officer 1st Class Eli Medellin, CJSOTF Arabian Peninsula, public domain, via DVIDS.

Our Mk12 Mod 1 clone build covers the quad railed rifle, and the Lone Survivor Mk12 build the film's.

Mk12 Mod H parts list: the issued part and what to buy

We cross checked one enthusiast Mod H parts list slot by slot and fixed its spelling in the third column.

The Mod H clone parts we stock, laid out overhead. Product photography is supplied by the listed merchants through their affiliate feeds.

Exact is the same part or its current version, and equivalent a product doing the same job. No source documents the magazine, sling or light.

The lower receiver group

The issued lowers were select fire, so your clone parts ways here.

Lower receiver: A1 profile, as on the Mod 0

Owners say rebuilt rifles kept their M16A1 lowers, and SADJ lists no lower change. Select fire lowers are machine gun receivers, so H&R's Retro M16A1 lowers give you the A1 profile in semi auto.

The H&R card is an equivalent, and PSA's A2 lower is the budget pick.

Trigger: a semi auto two stage for the issued group

SADJ lists Accuracy Speaks full auto triggers, and owners add KAC and Geissele SSF select fire groups. None belongs in your semi auto lower, so we card Geissele's SSA from the enthusiast list.

The G2S and MBT-2S are budget picks. A standard safety replaces the M16 selector.

Stock: ACE M4 SOCOM or LMT SOPMOD

SADJ names the ACE M4 SOCOM stock. Owners add LMT SOPMOD and Magpul stocks and say early ACE stocks wore at the notches.

DoubleStar's A150 is its current ACE M4 SOCOM stock, so we card it as exact, but it's out of stock. BCM's Gunfighter is the budget pick, and each needs a carbine receiver extension and buffer.

Grip and trigger guard: A2 and GI

The enthusiast list gives an A2 or Ergo grip and a GI guard, and owners add the Sierra SPR among others. No official source covers either.

The upper receiver group

Most of the 2007 changes sit here.

Upper receiver: Colt flat top, AF or keyhole forge

Owners read the rebuilt rifles' uppers from photos as Colt flat tops with an AF forge mark. No listing states a forge mark, so these are equivalents, and YHM's is the budget pick.

Barrel: 16 inch Douglas or Noveske, mid length gas

SADJ documents a 16 inch Douglas at 1:8, and owners tie FDE Noveskes to rebuilt rifles. We don't stock a Douglas AR barrel, or the Mod H barrels Wet Worx, Centurion Arms and Charlie's sell.

Noveske's 16 inch Recon gives you mid length gas at 1:7, but its listing doesn't mention the collar step, so it's an equivalent. Ballistic Advantage's Ops 12 is the budget pick, in .223 Wylde.

Gas block: PRI low profile or Badger Mk12

PRI's .750 low profile block carries SADJ's part number, 05-075-01, and the enthusiast list adds Badger Ordnance's Mk12. Both are exact, and you'll want a mid length tube. Skip tubes sold today as intermediate length; that's a longer system.

Muzzle device: AE brake with the long collar

The brake is also the suppressor mount. SADJ lists new OPS brakes and sleeves, and PRI's commercial Mod H shipped with an AE brake and collar.

Otter Creek's brake and collar are out of stock equivalents, and Precision Armament's M11-SPR only looks the part. We don't stock PRI's AE brake yet.

Handguard: PRI Gen III rifle length with the Recce rail

SADJ lists a PRI Gen III rifle length forearm, 05-073-03. Owners say rebuilt rifles wore it in FDE under PRI's shorter Recce rail.

Both forearms are exact, but you won't find one in stock with us today. PRI's Recce rail is in stock in FDE and black.

Bolt carrier group: M16 carrier with new bolts

SADJ says new bolts went in with the barrels, and owners name Colt or other M16 carriers. An M16 profile carrier is legal in your semi auto rifle.

Colt's is out of stock, so BCM's M16 group is the in stock match, and Toolcraft's is the budget pick.

Charging handle: PRI Gas Buster with military latch

SADJ lists new PRI Gas Busters, 05-0031, and owners specify the military latch. The combat latch version is an equivalent.

Optic, rings and iron sights

Owners say the glass and rings carried over from Mk12 service.

Optic: Leupold Mark 4 MR/T, carried over from the Mod 0

Owners and the enthusiast list name the Leupold Mark 4 MR/T 2.5-8x36, which Leupold calls the TS-30A2 and says served on the Mk12 Mod 1. It's out of production.

The Mark 4HD gets you a current Mark 4 with a TMR reticle. The VX-3HD is the budget pick, but its 1 inch tube won't fit 30mm rings.

Scope mount: ARMS #22 rings without lever stops

Owners list ARMS #22 mediums, Nightforce A107s and others on the Recce rail, and LaRue LT-104s without it. The enthusiast list specifies #22s without lever stops, and ARMS no longer makes those.

The A107 is the owners' Recce rail ring, and the ARMS #22 High is their pick without the rail. Warne's Maxima mediums are the budget pick. The current #22 medium has lever stops and was out of stock, and we don't list the LT-104 yet.

Front and rear sights: PRI flip ups on the Recce rail

SADJ documents a PRI rail mounted flip up front sight, 05-0028. No record names the rear, and owners say backup irons were rarely used.

PRI's 05-0028 front comes in black, out of stock, and FDE. Its matching rear and the front and rear sets are PRI's kit sights, and the Magpul and ARMS sights are budget stand ins.

Suppressor, laser and bipod

These bolt on last, and the can needs a check of your state's law first.

Suppressor: OPS Inc 12th Model or the AE AEM5

The OPS Inc 12th Model is an over the barrel can built for the Mk12, and SADJ's new OPS brakes imply the rebuilt rifles kept it. The Firearm Blog calls Allen Engineering's AEM5 its equivalent.

Otter Creek's OCM5 is an out of stock equivalent, and we don't stock the AEM5 or 12th Model yet.

Laser: on the parts lists, never confirmed

Only the enthusiast list and pages copying it name an AN/PEQ-15 or LA-5, and we found no photo or document tying a laser to the Mod H.

The ATPIAL-C is the commercial PEQ-15 housing, and the DBAL-A3 is an in stock equivalent.

Bipod: Harris swivel on a KAC mount

Owners and the enthusiast list give a Harris S-BRM on a KAC mount with a KMW Pod-Loc, or an Atlas BT10. We list the Harris, the Pod-Loc (out of stock) and the Atlas, but not KAC's mount. The ARMS #32 and LaRue LT130 are equivalent Harris mounts, and the Midwest Industries adapter is a budget stand in.

What you can buy today and what is unobtainable

Most of the rifle is in stock. The PRI forearm and OPS/AE brake are the hard parts.

Mk12 Mod H parts in stock on GPP today

We priced the closest in stock card per slot on 27 September 2026, and the cards show live prices.

The total skips the forearm, Recce rail, brake, suppressor, bipod, laser and small parts. Mk 262 77 grain was the Mk12 family load, so commercial 77 grain match is your stand in.

Discontinued parts and what to use instead

Six issued or reported parts are off the table for a civilian clone.

Complete Mod H rifles and uppers

PRI sold Mark 12 Mod H rifles in both twists, each $2,038 in an October 2021 capture, plus a DIY kit of its Mod H parts. Charlie's Custom Clones lists a PRI built Mod H rifle and a 16 inch barrel kit, and we don't stock either yet.

Our closest is BCM's 16 inch mid length upper with PRI's Gen III handguard, minus the stepped barrel and Recce rail.

For related builds, see our SEAL Recce rifle clone and M4A1 URGI clone build.

What the internet gets wrong about the Mk12 Mod H

Most Mod H pages repeat one parts list and a few retailer claims.

Mod H does not mean Mod Heavy

Only Wet Worx's Cloner's Corner says Mod Heavy, on a page that also calls the rifle 18 inch. Wet Worx's own Noveske barrel page says Holland.

The gas system is mid length, not rifle length

Wikipedia's rifle length claim cites a Charlie's product page. PRI's page for the same rifle says mid length, and so does SADJ.

Barrel maker and twist: only the 2007 Douglas is on record

SADJ's Douglas barrels were 1:8. For the Noveskes, the enthusiast list says 1:8, while the AR15.COM thread starter agreed the originals were 1:7.7. Noveske's 2025 barrel is a new product, and its marketing offers no documents for its 2007 origin story.

One parts list, copied by other sites

Allen Engineering's Mod H page repeats the enthusiast list down to the KWM typo. Wet Worx's list matches almost line for line, so the three count as one source.

No source for the 18 inch, 2,000 rifle story

The same Wet Worx page claims 18 inches, Marine Scout Snipers from 2011 and 2,000 rifles by 2015, citing nothing. SADJ counts 12 rifles in 2007, and the SAM-R the page mentions is a separate Marine rifle, covered in our USMC SAM-R clone build.

The civilian legal path to a Mk12 Mod H clone

Build it semi auto on a 16 inch barrel, and only the suppressor is an NFA item.

Semi auto lower and trigger instead of the issued M16 parts

Your clone has to be semi auto unless you build on a registered, transferable machine gun made before May 1986. Don't put an auto sear or any M16 auto part in your lower.

Why 16 inches needs no SBR paperwork

A 16 inch barrel meets the federal minimum, so you won't need SBR registration. Measure yours to confirm, counting a muzzle device only if it's pinned and welded. Owners' 10.5 and 12.5 inch Mod H inspired rifles are SBRs. ATF announced on October 9, 2026 that it would stop enforcing SBR registration, but check your state's law before you build one.

Suppressor transfer, IR lasers and state law

ATF announced on October 9, 2026 that it would stop enforcing NFA approval and registration for suppressors, so your can no longer needs an approved federal transfer. The brake and collar never did. Our suppressor guide for 2026 covers the tax. Issued IR lasers are generally sold only to military and law enforcement, and your state may restrict suppressors, barrel length and features.

Sources and photo credits

Every fact above comes from these sources. We cross checked an enthusiast parts list, which most Mod H pages copy.

Reference photos: what is verified and what is not

We found no public domain photo of a verified Mod H, and the clearest Rawah photo shows a Mod 1's quad rail.

The same Special Forces soldier behind a Mk12 at sunset in Rawah, Iraq, on 7 September 2007. The DVIDS caption identifies the rifle, but its forearm can't be made out in this light. U.S. Navy photo by Petty Officer 1st Class Eli Medellin, CJSOTF Arabian Peninsula, public domain, via DVIDS.

We host no forum or enthusiast gallery photos, since none carries a traceable credit.