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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


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As of 16 May 2024, Ron Allen is still making custom parts for his suppressors:

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Midway has it for a good price and free shipping right now. Just picked up 500 rounds to test out.

ETA for page ownage
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Pulled the barrel on my Mod 1 yesterday to refinish it in KG 2401F to match the late production rifles. Also sporting a 2007 production issued Leupold 2.5-8x36 TMR that I paired up with some NOS 2006 Butler Creek caps. I think I've done everything as faithfully as possible.

Not much else to go now before it's 100%. Still need to find the proper handguard (SR-15/16 FF RAS with the smaller text) and the proper USMC Pelican 1700 instead of this earlier 2004 one. Maybe even an Ops Inc can someday. AEM5 is still in jail, expecting at least another 4 months or so.

Very well done!!!  I wish I knew you were looking for that handguard a few days ago.

Because pic thread

Excellent posts lately, beautiful builds.

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Took the Mod 1 out in the snow this morning to zero with the new scope and re-barrel. I think it can still shoot better than I can.

Anyone need a pod loc? Have a spare lookalike I rigged up from an EABCO S Lever (same lever used on the gen 1 pod locs) and a misc spacer. Happy to mail it to anyone that could use it.



Also getting ready to part with a round illum housing Leupold 2.5-8 if anyone is looking right now. And just to keep the pics coming...

I spy…. Lookin good!

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Heavy breathing intensifies

Modernized Mk12s are hot AF

Anyone know where I can get one of those STORM IIs?

How much are you wanting to pay?

Presumably, raptar price?

For those of you using StrelokPro, which reticle in the options is the Leupold MK 4 3.5-10 SFP with MOA turret? Is it a simple mildot reticle? I have the Mk 3 168gr .308 turrets on with 1MOA elevation and 1/2MOA windage turret adjustments?

Shooting a DMR match in June so I need to get StrelokPro setup for the reticle and dialing with my 77gr TMK handloads.

ETA: and what are folks getting as far as height over bore for the Mk 4 in ARMS 22s and the PRI rail? I was getting 2.980” with my calipers, but happy to see what others have from their own rifles and/or an official source.

ETA2 pic thread

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Measure from center of rings to center of BCG.

Should just be a mil dot reticle unless you have the football mil dots. Then closest would be USMC mil
Dot.

I wouldn't bother with reticle on there. Just set your table up with your data. Shoot to confirm, then print it and tape it to your stock in 50m increments.

Yep, that’s how I measure to figure out height over bore; just wondering if others have done the same to get some more data.

Looks like the standard USMC MILDOT reticle so that’s what I’ll roll with. I’ll print the reticle pic for the stock for use on larger targets, but these matches will often have targets as small as 1MOA, or smaller, so dialing has to come into play especially if there’s a limited round count.

Going to take the SVD as well to ensure I come out near the bottom when competing against guys with modern 6.5 Grendel’s, 6ARCs, and 6-25x MRAD optics

Interesting.  If you zoom in on the top photo it almost looks like a clamp on gas block.

Pretty sure it's just canted over far enough to see the set screws on the bottom.

Dude is using the offset here, so its probably bottom of the gas block tbh

Yep, on second look you’re right.  My eyes really saw that differently.  

Mr. Stoner, forgive me for what I’m about to do.

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Don't worry he approves.

Debating on switching from the SOPMOD stock back to the A1 stock for my Mod 1. Just love the look, but I am not sure what I want to do.

All done and curing in the basement.

Started with a light tan base

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Then on goes the laundry bag. We actually had one from our upright hamper get a rip in it a few weeks back so I took it as a sign

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Doing this with the rifle on the bipod lead to some of the ‘poor man’s Kryptek’ pattern being more splotchy due to the bag not being in close contact with every part. I still like me it as it increases the randomness as some areas have the bag pattern while others have more of a general misting of the two shades of green and darker brown done with the bag on.

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Do it
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That is Bad Ass!

Took the Mk12 out today to try a few different ammo types. I feel like I could of did better I was kind of rushing shots since it was starting to rain harder and there was some heat mirage coming off the barrel and suppressor

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What rings are those? Scope looks higher than Hunter Biden

Thanks. This was my first rattlecan job, so I’m hoping the Gordon build is a little better once the F4 for the can comes back. That’ll probably come back in Dec/Jan, of course, so no painting until this time next year.

ARMS 22H

Two mk12s out in MI today. Where in MI are you? I’m on the west side of the state.

Was shooting IMI 77gr. Easily grouped under an inch if I did my part. Was slapping steel out to 500m with ease. Had the drone out spotting for me.
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I'm out in the East side in Chesterfield. I wish my barrel liked imi 77gr more.

Try a 75gr BTHP offering.

Frontier match 75 was always a good shooter for me when I didn't want to reload

It really likes the AAC 75gr BTHP.

Going to do more test later when it's warmer. Have a bunch more ammos to test, and I want to test them in my 14.5 and 12.5 too so I can find out what to stock up on

Anyone tried the Freedom Munitions 77gr stuff? It’s pretty cheap and has some decent reviews.

How is everyone dealing with the eye relief with an A1 stock and Mk4 MR/T 2.5-8x36mm, it seems like you have to get right up to the scope to have a full picture once you hit about 6x.
Its the only reason I am debating on keeping the SOPMOD is because I can collapse it an get closer.

FWIW, I chrono'ed a handful of loads (sample size of 5 rounds) to include some AAC loads from a 16" Mod H Centurion barrel and a magneto speed 3, in the following conditions per the kestrel - 67 degs F, 29.52inHg, 36% humidity, 369ft elevation...

Some of the 75gr:
75gr Frontier
AVG: 2599 SD: 9.1

75gr TAP T2
AVG: 2705 SD: 25.4

75gr AAC
AVG: 2544 SD: 56.1

For some of the 77gr:
77gr BH TMK (red box)
AVG: 2705 SD: 7.8

77gr BH Mk262 Mod 1C (brown box)
AVG: 2684 SD: 15.1

77gr AAC (nonSMK) lot ending in 291
AVG: 2688 SD: 34.8

77gr AAC (nonSMK) lot ending in 121
AVG: 2587 SD: 23.6

9 IN STOCK AEM5’s 20% off
$680 before transfer/shipping and taxes (if applicable)


https://modernwarriors.com/product/allen-engineering-aem5-5.56mm-suppressor-black

Use code: onlycans

**Didn’t realize these were getting easier to come by, theres a few venders that have them in stock. But 680 still looks like the best deal to me.

Are you more of a 'squared up' stance shooter? Turn your body in and you can get closer to the receiver.

I don’t have that scope, but I do have an A1 stock on my Mod 0 and ‘putting the plate towards the enemy’ aka squaring up does make it easier for me to get good eye relief on the Loopy 3.5-10x

Did PRi stop making their 18" barrels? Just noticed they weren't on the site anymore.

the newer Utah made ones would likely be cheaper would be my guess.

What offset rds they using?

Looks like an RM01 (non-adjustable RMR) to me.

As far as “modernizing” the Mk12 what is needed?  Optics, mounts?  I’m thinking of updating mine.  Currently mine sits in a traditional Mk12 Mod1 USMC setup.

Just put a mk5 in a badger on it.

Copy.  Splitting hairs between Badger vs. Geissele?

Actually it appears that most in the wild guys are running the leupold mark ims, but I'm pretty sure I've seen some badgers too. I don't recall ever seeing geissele.

Trajectory and Ron use the same price sheet. MSRP, MAP are the same regardless. The markings are identical except for the state and the cans are identical. They are both made exactly the same. one says Allen engineering utah and one says allen engineering nevada. 680 is under MAP. Way under. There are many dealers with these in stock. They are definately catching up. I think we have 2 left. I order from Trajectory because its quicker and I would like Ron making M24 and M4 (Gordan) cans instead of AEM5's

Are the ones linked Nevada or Utah cans? I did not see where it stated that. As I mentioned they both say Allen engineering. I put that info in the description on our website just so people know but again the cans are identical. That was the whole point.

I meant as in people will pay a premium for the older marked ones.  Just like they do to get an ops inc made one.  You will likely see a lot of the newer ones around that price.

Ah gotcha. I can see the idea of paying for an ops inc one. But paying more between Utah and Nevada I can’t really understand but to each his own. Here are a few comparisons. The engraving is deeper on the Utah cans. The knurling is a more consistent pattern. I’m going to ask about that. Attached File
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