Spe­cial Pur­pose

How we built our own Mk12 Mod 0 SPR mil­i­tary ri­fle replica

Firepower - - CONTENTS - TEXT & PHO­TOS BY JOHN SCOTT

Amove­ment in the firearms world that’s been rapidly gain­ing mo­men­tum with col­lec­tors and en­thu­si­asts over the past few years is the repli­ca­tion of mil­i­tary spec firearms. Whether you are seek­ing to recre­ate the carbine you were is­sued while in the ser­vice, or want to clone the ri­fle of a hero, recre­at­ing a par­tic­u­lar model or vari­a­tion of a ri­fle or pis­tol to the ex­act spec­i­fi­ca­tions of a mil­i­tary-used weapon can be both a chal­leng­ing and re­ward­ing ex­pe­ri­ence. When se­lect­ing a project to tackle, AR-15 en­thu­si­asts in par­tic­u­lar have many ri­fle vari­ants to choose from, thanks to its use as Amer­ica’s pri­mary mil­i­tary-is­sued ri­fle for more than half a cen­tury. From the Viet­nam-era M16A1 to to­day’s front-line M4A1, there are many AR-15 vari­ants one can base a build on.

Build­ing a Clone

“The Mk12 is a cur­rent is­sue M16 based ri­fle that is fielded by U.S. Army, Navy and Marines spe­cial op­er­a­tions units.”

We should men­tion that when we say clone, we mean to repli­cate, within rea­son, the com­po­nents, attachments, ac­ces­sories of a par­tic­u­lar type of weapon used by the mil­i­tary at a par­tic­u­lar point in time. How de­tailed it gets is up to the builder and his bud­get. The sky’s the limit!

We be­lieve that some near-im­pos­si­ble items to pro­cure such as re­ceivers or ac­ces­sories that are no longer made or at­tributes that are dif­fi­cult or not pos­si­ble to at­tain, such as se­lect fire ca­pa­bil­ity, may be re­placed with al­ter­na­tives. (Then again, we’re more for­giv­ing than some of the ded­i­cated die-hards out there.) But scor­ing long out of pro­duc­tion and hard-to-find items on the se­condary mar­ket is also a part of the fun of build­ing a clone. The search goes on!

U.S. Navy Mark 12 SPR

Out­fit­ted with an ac­cur­ized bar­rel, us­ing a tele­scopic sight and match am­mu­ni­tion, the Navy’s Mark 12 Spe­cial Pur­pose Ri­fle (SPR) is cur­rently one of the most pop­u­lar ri­fles for en­thu­si­asts to repli­cate. Orig­i­nally de­vel­oped by United States Spe­cial Op­er­a­tions Com­mand as an up­per re­ceiver kit to help sup­ple­ment its car­bines, the pro­gram even­tu­ally evolved into a com­plete weapon sys­tem. The Naval Spe­cial War­fare Cen­ter, Crane Divi­sion, helped de­velop the Mk12 into its fi­nal form.

With­out get­ting deeper into its his­tory (which can be quite con­vo­luted and far more de­tailed than we have space for in this ar­ti­cle), we’ll go over its ba­sic specs. There are sev­eral Mk12 vari­ants, with the Mod 0 and Mod 1 ver­sions be­ing the most com­mon. The Mk12 is a cur­rent-is­sue M16-based ri­fle that is fielded by U.S. Army, Navy and Marines spe­cial op­er­a­tions units. You might rec­og­nize the Mk12 as the ri­fle used by Navy SEALS Chris Kyle and Mar­cus Lut­trell as por­trayed in the books and movies Amer­i­can Sniper and Lone Sur­vivor, re­spec­tively.

At its heart, the Mk12 has an 18-inch

416R stain­less steel bar­rel that fea­tures a ri­fle-length gas sys­tem. The bar­rel has a spe­cial “SPR” pro­file that al­lows for an OPS Inc. col­lar to be in­stalled on it. An OPS Inc.

“There are sev­eral Mk12 vari­ants, with the Mod 0 and Mod 1 ver­sions be­ing the most com­mon.”

muz­zle brake is also in­stalled on the bar­rel so that it can fit the com­pany’s 12th Model Sup­pres­sor. The Mk12’s bar­rel was de­signed to fire the Mk262 car­tridge, which uses a match-grade 77-grain bul­let.

True mil­i­tary Mk12s are com­monly found with M16A1 or M4A1 full-auto lower re­ceivers. Most peo­ple repli­cat­ing the Mk12 choose to go with com­monly found forged semi-auto AR-15 low­ers in­stead. For those look­ing for an even more authen­tic look, Brownells, in con­junc­tion with No­dak Spud, of­fers an M16a1-con­toured lower re­ceiver that they call the BRN-16A1 that closely re­sem­bles the M16A1 but with semi-auto ca­pa­bil­ity.

Ac­ces­sories found on Mk12s vary widely de­pend­ing on the in­di­vid­ual end user and in which time pe­riod it was used. For th­ese rea­sons, Mk12 clones can dif­fer from one an­other, even ones that are built to be as pe­riod-cor­rect as pos­si­ble.

Fo­cus on Mod 0

Re­mem­ber we men­tioned that the his­tory of the Mk12 can be con­vo­luted? That’s be­cause the ri­fle wasn’t de­vel­oped all at one time. Us­ing parts of used M16A1S along with other sup­ple­mented parts, the Mk12 was de­vel­oped over a span of a few years. This makes track­ing ex­actly how Mk12s were con­fig­ured a bit mud­dled to say the least.

“Ac­ces­sories found on the Mk12 vary de­pend­ing on the end user and the time pe­riod in which it was used.”

De­pend­ing on which vari­ant Mk12 you wish to build, its ac­ces­sories—such as hand­guard, grip, trig­ger and even back-up iron sights— will dif­fer. In this ar­ti­cle, we fo­cus our build on the Mk12 Mod 0, which is cur­rently out of ser­vice and has been re­placed by the Mod 1. There are plenty of on­line sources that can help you delve deeper into the ex­act­ing de­tails of what qual­i­fies a Mk12 as a Mk12 and the de­tails of its dif­fer­ent vari­ants.

FDE Clone

We built two Mk12 Mod 0 clones by go­ing with two dif­fer­ent meth­ods and ended up with two slightly dif­fer­ently con­fig­ured ri­fles.

The flat dark earth (FDE) ri­fle pic­tured here was built us­ing a com­plete up­per we ac­quired from Pre­ci­sion Re­flex, Inc. (PRI). PRI has been sup­ply­ing parts to the Mk12 pro­gram since the be­gin­ning and has staff that helped with its de­vel­op­ment.

The PRI 18-inch Mark 12 Mod 0 SPR Gen II up­per comes fac­tory-built to Mk12 spec­i­fi­ca­tions and in­cludes an 18-inch, 5.56x45mm cal­iber Dou­glas 416R stain­less steel bar­rel with a 1/7 twist rate. It comes with PRI flipup front gas block front sight and rear flip sight, ri­fle-length gas tube, a PRI Gas Buster charg­ing han­dle with big latch, and an OPS Inc. brake and col­lar. The up­per is com­pleted with a PRI Gen III ri­fle-length car­bon fiber free-float fore­arm that is Cer­akoted in FDE fin­ish. It is topped with a PRI full-length top rail with PEQII re­mov­able rail sec­tion.

Typ­i­cal of build­ing a clone of a ri­fle that has since been out of use, we had to use a newer model of an item that has gone out of pro­duc­tion. Sit­ting atop the up­per is a Le­upold Mark 4 2.5-8x36 MR/T M2 (112633) scope, which ac­cord­ing to our re­search is the clos­est cur­rent pro­duc­tion op­tic to the orig­i­nal Le­upold TS-30 or TS-30 A2 scopes that were orig­i­nally used on the Mod 0. The scope sits in A.R.M.S. #22 Medium rings that are equipped with a #22 Tac­ti­cal Ring Cap and a #22 Tac­ti­cal Ring Rail. It also sports a Har­ris HBRMS Bi­pod in A.R.M.S. #32 throw lever bi­pod adapter.

Com­plet­ing our FDE clone is the afore­men­tioned cus­tom Cer­akoted Brownells BRN-16A1 lower that closely re­sem­bles an M16A1 lower’s con­tours. We fin­ished it off with a Brownells AR-15 lower parts kit, an Ergo Sur­grip, PRI A2 stock as­sem­bly and Geis­sele SSA-E two-stage trig­ger.

Pieced To­gether

For the black-col­ored clone, we took a dif­fer­ent build ap­proach. We de­cided to as­sem­ble the Mk12 Mod 0 up­per from the ground up, sourc­ing what parts we could from what is cur­rently in pro­duc­tion. Again, we looked to­ward PRI for some of the ma­jor parts in­clud­ing the 18-inch Dou­glas 416R stain­less bar­rel in a black fin­ish. We also got other PRI Mk12 Mod 0 sta­ples such as their Gen II Retro Car­bon Fiber ri­fle-length fore­arm, G2 flip-up front gas block front sight and M84 Gas Buster big latch charg­ing han­dle.

Com­plet­ing the up­per re­ceiver as­sem­bly is a BCM M4 up­per re­ceiver, Allen En­gi­neer­ing AEMB brake and SPR col­lar (word on the street is that Allen makes them for OPS Inc.), Strike In­dus­tries ri­fle-length gas tube

“We de­cided to as­sem­ble the Mk12 Mod 0 up­per from ground up, sourc­ing what parts we could from what is cur­rently in pro­duc­tion.”

and Brownells M16 ni­tride-coated bolt car­rier group.

Ac­ces­soriz­ing the up­per, we opted for an A.R.M.S. #38 S-EX Swan Sleeve and #40L low-pro­file rear sight, which are what many orig­i­nal Mod 0 ri­fles were out­fit­ted with. Again, in­stead of scour­ing the se­condary mar­ket for an orig­i­nal scope, we opted for a cur­rent day con­tem­po­rary. The Le­upold Mark 4 LR/T 3.5-10x40mm (67945) has an il­lu­mi­nated Mil Dot ret­i­cle and is out­fit­ted with their M3 tur­rets. It sits in the same A.R.M.S. ring setup as our FDE Mk12. A Har­ris Bi­pod with A.R.M.S. #32 bi­pod adapter rounds out the up­per as­sem­bly.

For the lower half, we went with an An­der­sen Ma­chine forged lower re­ceiver com­plete with Brownells lower parts kit. To stay true to the Mod 0 build theme, we in­stalled a Knights Ar­ma­ment 4.5-pound 2-stage match trig­ger, the same trig­ger that many orig­i­nal Mod 0 ri­fles used. We also sourced an Ergo grip and an A2 stock as­sem­bly by UTG to com­plete the build.

Dif­fer­ence in the De­tails

Mi­nus the color, at a glance the two Mk12 Mod 0 clones look just about iden­ti­cal. But

to the dis­cern­ing eye, you’ll no­tice some vis­ual cues that set the two apart. The main dif­fer­ence be­comes ob­vi­ous when you study the top rails and rear sights on the up­per re­ceivers. The FDE ri­fle fea­tures a PRI top rail and rear sight while the black ri­fle uses ones by A.R.M.S. For those keep­ing score, the A.R.M.S. ver­sion is more cor­rect for a Mod 0 clone ac­cord­ing to our re­search.

You’ll also no­tice that the col­lar on the FDE ri­fle is a bit shorter than the black ver­sion and that its setscrew faces 12 o’clock while the black one has its setscrew fac­ing 6 o’clock. Which one is cor­rect? Per­haps both. More re­search will be re­quired. As you can see, build­ing a clone re­quires plenty of re­search and ded­i­ca­tion if you want to get ev­ery de­tail right.

“With our clones com­plete, we ad­mired their beauty and promptly headed off to the range to re­ally en­joy them.”

There are many AR-15 vari­ants one can choose to clone. The Mk12 Mod 0 is a pop­u­lar choice.

The Mk12 Mod 0 uti­lizes an 18-inch, 5.56 cal­iber Dou­glas 416R stain­less steel bar­rel and a PRI Gen II Retro Car­bon Fiber ri­fle-length fore­arm.

Right: Allen En­gi­neer­ing’s AEM5 si­lencer is a pop­u­lar equiv­a­lent used on many clones.

Far Right: A proper Mk12 clone uses A.R.M.S. #22 scope rings, ring cap and ring rail for its scope mount.

Far Right: Pri’s M84 Gas Buster charg­ing han­dle is cor­rect for Mk12 builds.

Right: Mk12s were orig­i­nally is­sued with OPS Inc. 12th Model Sup­pres­sors.

Right: Our clones use dif­fer­ent top rail sleeves. The FDE uses a PRI full-length top rail while the black one uses the A.R.M.S. #38 S-EX.

Sourc­ing all the parts to as­sem­ble the Mk12 Mod 0 up­per from the ground up can be a chal­lenge, but is def­i­nitely worth the ef­fort.

Although both of our Mk12 Mod 0 clones look sim­i­lar, to the dis­cern­ing eye, you’ll no­tice some vis­ual cues that set the two apart.

Orig­i­nal Mk12’s use Colt M16 A1 se­lect-fire lower re­ceivers sim­i­lar to this Colt M16 A2. Note the full-auto fire trig­ger group.

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