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The following parts lists and substitution parts was compiled by lancecriminal86 over the course of a LOT of research. Read up and pay attention!

Below are the 100% .mil-spec parts lists to build a true SPR or Mk12 clone. Some of these parts are no longer manufactured and will require much effort and money to locate through forums and online brokers. Keep in mind the rifles were built off donor M16A1s, hence the prevalent A1 parts in the lower receivers and the BCGs. They were also first configured using parts available from 1998-2004, and most are inferior in some ways to newer designs. If this bothers you too much, STOP NOW.

The rifles were issued as a kit in a Pelican 1700 case with cutouts. The kits included the rifle with suppressor, optic, bipod, an Eagle TAS-1 UMSS sling (unobtanium and also absolute crap), with a Dewey 1-piece cleaning rod plus Otis cleaning kit, and a cutout for magazines. An operator's manual was also included, however these have not been officially released for public consumption. However, the manuals are out there, and some companies building Mk12 uppers include one. Whether these are official .mil operator's manuals or specially made is currently unclear as the manual itself still contains language that it is not for distribution.

- Alternate .mil-spec parts due to NFA, NLA parts, or changes in name/markings for current production in [brackets]

- Extra notes about parts or availability are in (parenthesis)

LOWER
Lower receivers were standard across the SPR/Mk12 variants and the only variations would be between grips, stocks, and buffers. Most were marked either Colt or GM Hydramatic. All other parts were the same in regards to the lower parts. One caveat is the trigger, as the program originally selected the Knight's Armament 2-stage Full Auto Match trigger. Later on, some issues regarding negligent discharges occurred, and Geissele SSF triggers ultimately found their way into the Mk12 family. Whether 100% of all Mk12s eventually received the Geissele trigger isn't clear, so either is acceptable.

• Lower: M16A1 pattern [Nodak Spud NDSA1 or 80% re-profiled/finished/engraved]
• Trigger: Knight's 2-Stage Full Auto Match Trigger or Geissele SSF [KAC semi-auto Match or Geissele SSA/SSA-E]
• Grip: A1, A2, ERGO Original
• Stock: Originally issued with A1 stocks, both solid D and trapdoor E types; as A1 stocks dwindled, A2 were used; ModH rifles rebuilt with Ace SOCOM stocks
• Small parts: Standard M16A1 parts
  
  

UPPER
The upper receivers, which ultimately differentiate the four variants of the Mk12, have the most variation between each other.


Early SPR/Mod0

• Upper: Colt, Diemaco, or Armalite marked, flat top, M4 feed-ramps
• Barrel: Douglas 416r SS, 18" SPR contour, 1/7 twist, flats milled for PRi FSB (Compass Lake, Centurion Arms, High Caliber Sales, and PRi can all supply barrels that meet the appropriate spec minus FSB flats)
• BCG: Colt M-16
• Handguard: Precision Reflex Gen I carbon fiber free-float Handguard, rifle length (identified by button-head screws and one vent hole near barrel nut on lower half; no heat shields)
• A.R.M.S. #38 SPR MOD Sleeve (either the PEQ version or with uneven spacing on the front  but not the full 1913 railed version)
• FSB: PRi early folding front sight base and gas manifold, set-screw, with elevation wheel
• Charging handle: PRi Gas Buster M-84 with military latch
• Muzzle device: OPS Inc 12th Model brake/collar, and 12th Model suppressor [Allen Engineering AEM5 and brake/collar]
• Rear iron sight: A.R.M.S. #40
• Scope rings: A.R.M.S. #22 Medium rings, #22 Tactical Ring Cap and #22 Tactical Ring Rail (rings should not include "lever-stop" hump as produced later by A.R.M.S.)
• Optic: Leupold Vari-X III 3.5-10x40mm LR, M3 turrets, illuminated Mil-Dot reticle (use .308 turret) [Leupold LR/T 3.5-10x40 LR, M3 turrets, Illuminated Mil-Dot reticle]
• Bipod: Versa-Pod with A.R.M.S. #42, or a Harris with A.R.M.S. #32 (Versa-Pod far inferior to Harris)

Late Mod0

• Upper: Colt or Diemaco marked, flat top, M4 feed-ramps
• Barrel: Douglas 416r SS, 18" SPR contour, 1/7 twist, flats milled for PRi FSB (Compass Lake, Centurion Arms, High Caliber Sales, and PRi can all supply barrels that meet the appropriate spec minus FSB flats)
• BCG: Colt M-16.
• Handguard: Precision Reflex Gen III carbon fiber free-float handguard, rifle length
• A.R.M.S. #38 SPR-PEQ-2-3 Sleeve
• FSB: PRi folding FSB, set-screw, .750 (original production had PRi's full address engraved on sight tower; those engraved with "PRi USA" are later manufacture)
• Charging handle: PRi Gas Buster M-84 with military latch
• Muzzle device: OPS Inc. 12th Model brake/collar, and 12th Model suppressor [Allen Engineering AEM5 and brake/collar]
• Rear iron sight: A.R.M.S. #40
• Scope Rings: A.R.M.S. #22 Medium rings (rings should not include "lever-stop" hump as produced later by A.R.M.S.)
• Optic: Leupold 3-9x36mm TS-30, Mk4 MR/T 2.5-8x36mm TS-30A2, M2 turrets with Mk262 BDC, illuminated TMR reticle
• Bipod: Harris with either A.R.M.S. #32 or KAC RAS bipod adapter

SPR/A, SPR/B, Mod1

• Upper: Colt or Diemaco marked, flat top, M4 feed-ramps
• Barrel: Douglas 416r SS, 18" SPR contour, 1/7 twist, flats milled for PRi FSB (Compass Lake, Centurion Arms, High Caliber Sales, and PRi can all supply barrels that meet the appropriate spec minus FSB flats)
• BCG: Colt M-16
• Handguard: Knight's Armament M4 Match FF RAS, rifle length (now called the SR15/16 Match FF RAS)
• Gas block: NSWC Crane pattern (Badger Ordnance parkerized/NSN version is correct, has open front of gas tube hole)
• Charging handle: PRi Gas Buster M-84 with military latch
• Muzzle device: OPS Inc. 12th Model brake/collar, and 12th Model suppressor [Allen Engineering AEM5 and brake/collar]
• Scope rings: A.R.M.S. #22 High rings (A.R.M.S. rings should not include "lever-stop" hump as produced later by A.R.M.S.)
• Optic: Leupold Mk4 MR/T 2.5-8x36mm TS-30A2, M2 turrets with Mk262 BDC, illuminated TMR reticle or NightForce 2.5-10x24 (optionally with NightForce rings)
• Bipod: Harris with KAC RAS bipod adapter (BRM-S, A.R.M.S. #32 could still optionally be used)

ModH, Mod "Holland"

• Upper: Colt or Diemaco marked, flat top, M4 feed-ramps
• Barrel: Noveske 16" Recon, mid-length gas system, profiled for OPS Inc. 12th Model brake/collar (will require aftermarket contouring of most barrels)
• BCG: Colt M-16
• Handguard: Precision Reflex Gen III carbon fiber free-float handguard, FDE, rifle length
• Charging handle: PRi Gas Buster M-84 with military latch
• Muzzle Device: OPS. Inc. 12th Model brake/collar, and 12th Model suppressor [Allen Engineering AEM5 and brake/collar]
• Scope Rings: A.R.M.S. #22 Medium rings on PRi recce rail (rings should not include "lever-stop" hump as produced later by A.R.M.S.) or LaRue LT-104 SPR mount
• Optic: Leupold 3-9x36mm TS-30, Mk4 MR/T 2.5-8x36mm TS-30A2, M2 turrets with Mk262 BDC, illuminated TMR reticle, Leupold Vari-X III 3.5-10x40mm LR, M3 turrets, illuminated Mil-Dot reticle (use .308 turret) [Leupold LR/T 3.5-10x40mm LR, M3 turrets, illuminated Mil-Dot reticle]; S&B Short-Dot
• Bipod: Harris with either A.R.M.S. #32 or KAC RAS bipod adapter
• Iron sights: (apparently PRI were supplied but never used)
  
  

In the Wild
Naturally, once these rifles were issued to units, operators and even Marines used various non-issued parts. Here is a short summary of what has been seen:

Early SPR/Mod0:
Both Leupold 3.5-10x40mm and 3-9x36mm scopes have been used. Many have had carbine stocks like the old CAR-style, enhanced M4, SOPMOD Gen I, or even the Tactical DuoStock swapped on.

Mod1:
One 3rd SFG-issued rifle pictured with SSgt Robert J. Miller (MoH recipient) used an A.R.M.S #36 S-EX 5.56mm rail, and a Leupold M3X 10x fixed-power scope, possibly pulled from an M-24 or SR-25 rifle. Another has been seen with a Magpul PRS, LaRue mount, and a Premier Reticles 3-15x used by an AMU shooter, and a similar rifle was pictured on a FOB in a very posed-looking photo. Further, a USMC-issued Mod1 was seen using #22 Medium rings instead of High rings, and a LaRue mount has been spotted as well. Grips have varied from the usual A1, A2, and ERGO, and at least one Magpul MIAD has been used. As with the Mod0s, carbine stocks like the SOPMOD and M4 have been used on Mod1s.

ModH:
The Mod "Holland" was already a small-batch configuration, but even as soon as they were issued to 5th SFG units, some Ace SOCOM stocks were replaced with Magpul ACS and CTR stocks. Optics are basically anything existing in the unit's inventory, from S&B ShortDots still in the system, the 3-9x and 3.5-10x Leupold scopes from earlier Mod0s, and there's even a photo of an ELCAN on a Mod1 floating around. No non-magnified optics like EOTechs or regular Aimpoint M2/M4s, but Micros have been seen on offset mounts. Backup iron sights, as a whole, were almost entirely left unmounted. Grips were again the same usual selection.

Parts Alternatives for Clone Building
Many parts are rare, expensive, and/or both. Despite this, there are some alternatives to a 100% pure clone that will still provide the same visual look and performance. While not a museum-grade clone, most would be hard-pressed to discern the difference. Just know there are those of us out there that will haze and peer-pressure you into further moving your build towards a true clone.

Barrel:
Popular options are the White Oak Armament SPR barrel (rifle gas), BCM's SPR barrel, Rainier's Match and Ultramatch offerings (ensure it's the SPR contour with 12th Model profile), Ballistic Advantage's SPR barrel. Compass Lake Engineering can also spin a Mk12 profiled barrel with a Criterion chrome-lined blank, or even a Krieger, which was one of the original contenders for the program. The DPMS Mk12 barrels are NOT properly profiled for a clone.

Optics & Rings:
In the case of the Leupold 3-9x or 3.5-10x, it's generally okay to go for a non-illuminated version of either, sometimes with M1 or other turrets and reticles. As far as the NightForce scope, the 2.5-10x24mm is not generally released to the public anymore (with one recent exception through Sniper's Hide), so many use the 32mm or even 42mm versions with the #22 High rings. As for the rings, any of the recent produced A.R.M.S. #22s with the lever-stop humps are functionally the same, the desire for non-lever-stops is purely aesthetic when going for the most authentic look. As LaRue LT-104s have been seen in use, it is justifiable to use one depending on whether you have a specific rifle you want to copy, or even just if you absolutely cannot acquire #22 High rings.

A.R.M.S. #38 SWAN Sleeve:
The #38 family of sleeves are no longer available. Finding them secondhand usually cost $250-$300 easy, more for rarer early variants. Fortunately, PRi's copies of the sleeves look and function almost identically, with minor visual differences. PRi and other builders supply these currently for complete Mod0 builds.

FSB:
While the set-screw version of PRi's FSB is spec, most use the cross-bolt, clamp-style version. They are extremely robust, and when aligned and torqued, have been shown to hold strong enough that you'll probably shear your barrel extension pin or upper before it budges. This is mainly how Mod0 uppers are supplied by most vendors, including PRi themselves.

Suppressor, Brake/Collar:
Diverging from the OPS Inc. or AEM brake and collar will get you MAJOR flak. Trust me, I've been running an AAC SPR/M4 for years now and it took a LONG time to not get clubbed every time I posted it. The Allen Engineering AEM5 is basically the current production of the OPS Inc. 12th Model, as they were originally made by Ron Allen and his team in the first place. Only minor differences separate original OPS Inc. cans from AE cans, and these are only obvious to trained eyes.

As far as the rest, you can swap Colt parts out for any other .mil-spec parts, like BCM, DD, CMT, etc. Any billet uppers/lowers, funky BCG coatings, extended bolt releases, etc. are extremely frowned upon. Remember, once you start going down the path of building a "better" rifle rather than what was spec, you're quickly beyond clone territory and would have been better off building a custom 16" or 20" rifle. Cloning is generally viewed as all-in or not at all.

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Complete Mk12 Mod0 / Mod1 Uppers
Bravo Company Manufacturing
High Caliber Sales
Precision Reflex Inc.

Specific Mk12 Tech
Augee's side-by-side comparison of the original ARMS SWAN Sleeve and PRI reproduction PEQ Sleeves: bottom of p136
KOBK's side-by-side comparison of PRI Gen I, II, and III handguards, and Gen I and Gen II FSBs, and SWANs: middle of p137
Augee's Mod1 gas block tech: top half of p357
Glass1's Early Mod0 photo breakdown: middle of p449
tamboi's Leupold Vari-X, TS30, and TS30A2 scope history/lineage, and part numbers, p.792

Attached File

Thank you sir

Edit page ownage: This is the progress I made last time I was home, love this rifle

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Anyone have the gas port size of a true SPR spec barrel? RLGS, of course.

My mk12.

Want to get 77gr dials made for my MK4, does anyone know the exact info from the MK12 Mod 1 77gr dials?

Aside from the correct verbiage, I think you'd be better off chronoing the rounds out of your rifle, entering your average atmospherics, etc. so the BDC is more apt to be correct.

Looking good brother

NF 2.5-10x24 Length = 9.9 in.
TS-30A2 (Mk4 MR/T 2.5-8x36) Length = 11.3 in.
NF 2.5-10x32 Length = 12.0 in.

I've got all three; that extra 0.7 in. on the x32 definitely matters.  I honestly can't remember what the issue was when I tried it out, but you have to make concessions to make it fit (i.e. losing the rear sight, pushing eye relief excessively rearward, etc.).

The x24 went on a SCAR 17 (mainly due to the FC-2 reticle) and the x32 ended up on a bolt gun.

Assuming you have the MR/T M2 turret scope at the moment, just call Leupold and tell them you want to buy the dials off scope model no. 112633.

Does anyone know when you order the PRI handgaurd, does it come with all necessary parts,  or do I have to order the barrel nut and ring separately?

Every one I've ordered comes with it.

Thanks!  Handgaurd and front sight being ordered tomorrow

Look, found a collar, it's time to build another mk12
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Dat CQ doe.

 
You know someone had to have fucked up if they have to tour the barracks every 15 minutes

I didn't do anything wrong duh    Sgtmaj made everybody do it. 2 guys had to stand duty for 48 hrs because they didn't log every 15       Pretty gay  but whatever  

Don't miss that bullshit.

Never stood barracks duty my entire enlistment

On topic Ron Allens a nice guy to talk with.  Just gotta wait on a new collar to fix my 2 rotations issue.

Nice first post.

Glad you eventually won the battle with your gas block.

My '02 CLE'd Douglas is .10"





Ejects at 3:30 consistently.





 

That book brings back some memories.

That won't work so well if you are trying to dial elavation.

Renovations in the new house are going well.
" />

I still don't know everybody's handle, but I'm assuming you are ones of the guys I frequently talk to in the clone fb group.

The issue I'm having now is I am way over gassed. Not bad enough.to rip the back of the casing off, but bad enough it is displacing the rim slightly.

Hopefully I can get that sorted soon.

X24 in the EE

http://www.ar15.com/forums/t_7_163/1527265_WTS_Nightforce_2_5_10x24_with_illuminated_NP_R2_reticle_and_zerostops__very_rare_scope.html

Wow....Brownell's getting into the clone game!

What's special about these dials? Instead of 1/2 moa adjustments, are they something different? Like 100 yard adjustments??

Also at a better price than the Nodak. But I like the Nodak minimal engraving better, hmmm.....

They have a BDC (ballistic/bullet drop compensation) etched on above the value in distance, and these are for the MK262 round. So say they have you zero at 100, and you need to get to 600 quick, just turn till the 6 is lined up. Of course something mass produced so to speak will only be so close. You'd be better off if you really want this choosing a load/projectile you want, entering the MV from YOUR rifle, your atmosphere conditions (again not a constant) and the rest of the data and having them built on that. For clone correctness you can have the appropriate verbiage engraved on the top.

So I finally had time to install the KAC hand guard on my BCM upper and I couldn't even get the gas block off. I was bending allen wrenches left and right so I dropped it off with a local gun smith and even after heating it up a little they still couldn't get it to budge.  They're keeping it over night to work their magic, hopefully they have positive results.  I've never had a problem removing a gas block, maybe a barrel nut, but never a gas block.  BCM must soak their gas blocks in loctite, haha!

Had the same problem a few weeks ago. Had to run a drill bit through the screws to break them loose. Barrel was untouched but destroyed the gas block.
BCM shit is crazy overbuilt, it's a good and a bad thing.

ugh, that is not what I wanted to hear, haha!  I hope they can get it off without wasting the gas block, I just don't want to have to order another gas block and wait for it to come in before I can put it back together.  

 

I've had to sit both BCM and ADCO installed gas blocks in the oven for 20 minutes and that normally does the trick for me.

At what temperature?

 

Is this running suppressed? Mine ejects consistently at 5 suppressed, but all I've been running so far is .223 55gr Winchester white box. Plus I forgot to size my gas port before zeroing my flip-up front sight gas block.

 
250-300 is good

MAP gas from Home Depot. About 10-20 seconds of direct heat and the set screws back out easily.  BCM does use high temp thread locker on their blocks.

I just went through this about two weeks ago with my BCM. I had to heat it up pretty good but once I did they came out with very little effort.

Un-suppressed with 77gr.
 

Solid ass first post there ;)

About time you joined!

Edit

Not quite there but I am working on them both. I have been testing out some rattle can patterns on some old mags. I think I am going to go ahead and paint the holland this weekend. I'm still having a hard time deciding on colors.

Crappy pic




HCS Douglas 16" Reece barrel
BCM Upper, Lower, BCG
PRI Reece Rail and Hand guard
MK4 3.5-10 M2 Turrets

Just got this from Leupold. Ordered it back in December. Called again in February and they sent this out. Part #112635 and it is a standard part. Not from the custom shop." />

Cost 30 bucks.

 
Can we get s aide shot?

Will the Nightforce NXS 3.5-15 F1 fit a Mod0 with Swan Sleeve and ARMS medium rings?

The external object diameter of the Leupold Mark 4 3.5-10x40 measures 1.832" and has a tiny bit more than 0.25" clearance between the objective and the Swan Sleeve.

A seller of a Nightforce NXS 3.5-15 F1 said the external objective diameter is 2.321". Can anyone throw a pair of calipers on theirs and confirm please?

If that 2.321" external objective diameter is indeed correct, then it should work. Has anyone tried to throw one in a set of ARMS mediums?

Your math is off. Those numbers leave you needing another .01".



With that setup, you can forget running lens caps, and I'm fairly certain the obj. bell is going to contact the sleeve anyway.



 

 
Yeah I don't think you're going to clear the 50mm objective with #22Ms. I have no math to back this up, just some near-figurin' with my eyeballs.

You should've stepped in and told him not to be a whack-ass busta and use a correct optic.



 

I second this

Third. Mk4 or gtfo here.

...now that I can say that lol.

And out the door I go.