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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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I’ve always liked the LT104 Mount.. Just something about it..

As the street wise would say: "I gotchu fam"



They seem to predominately be standard button FAs, but that one at least had a teardrop. But, that also may have been among the earlier Mod 1s our there as well.

Don't forget the long bottom rail.

Got my MOD 1 upper back from gunsmith (assembler). Currently waiting on lower parts kit to complete a proper A1 style lower.

It exploded

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More afterthoughts. Using barricades (like barrels) to support the gun from kneeling (for example), I think is where a handstop shines on these rifles. I know the XTM Handstop showed up on a Holland, and Knight's vert grips were mostly prevalent, as well as an AFG here or there...but the handstop just, works.

Using an XTM Handstop Kit on my MOD1, and it made life much easier to play with barricades...easier to find the happy place where you can stabilize the rifle, get a good purchase on it, and whatever it is resting on. Mind you, I didn't have an AFG or vert grip on this gun at any point to compare to, but I imagine having something much longer or bulkier hanging under it to have to work around would be a comparative pain in instances like that.

Also, I need a tripod. Pretty much convinced that will be my next big purchase.

ETA: Sig .223 77gr OTM ammo at $20 per 20, and Hornady Black 75gr HPBT at about $22 per 20, is great for cheap "match" loads to throw downrange. Didn't even break into my CBC 77gr or MK262 stuff...

Man, how is that cheap? Cheap match should be $0.50/round, expensive match is what you’re describing. I’ve usually seen that Black 75gr Match for $15-16/box. Haven’t tried it though.

1. XTM hand stop ROCKS.

2. I shoot 75gr OTM for .36/rnd. buying match ammo is a nope for me. for less than the cost of a case of match, you could roll your own.

Not quite as cheap, but for those that don't have the time/patience for reloading, CBC/Magtech 77gr SMK does very good for me and can be picked up for around .50/rd. Availability can be hit or miss though.

It always seems to be in stock at SG, and for the best price in bulk

Obviously they have their reasons, but why wouldn't the USMC stick with the Mk12 Mod1s they had in inventory already instead of picking a new designated marksman rifle?

Same Mk262 ammo, same KAC irons, same TS30A2 glass - what does this HK do better than the Mk12 in this DMR role?

New "M38" Squad Designated Marksman Rifle:

Hmm, one of those HKs with an Ops 12th/AEM5 would be an interesting animal...

It's called spending budget money so you don't lose it. That's my guess anyways. That and following in the footsteps of all these cool-guy units. The Mod1 was almost perfect. Shorten the barrel to 16", swap the handguard for a URX 3.1 or MLOK, and keep the indexing OPS cans until they're shot-out. Mk12 Mod1 redux.

I don't reload, so it's cheap enough for me. Shoot, the 75gr Black could be cheaper than what I posted. I typically just snag a box every so often when I need it, off the shelf locally.

This is what I need more of...tested 10 rounds of every match load (various 75  and 77gr) and the CBC was most consistent (and was the smallest group) versus everything else. This was excluding Black Hills 77SMK loads. But the 75gr and 77gr stuff I was burning up the other day worked so well out to 500, I didn't bother with shooting any CBC (or MK262 for that matter). That, and I don't want to get used to making wind calls like I had to on the real good stuff. Trying to make hits on 700 without being able to see splashes was nigh impossible.

Agreed 100% on the 16” Mod 1 with some weight reduction in mind. I don’t see what else you would be wanting in a rifle.

I know it’s pretty new and maybe that’s not a finalized rifle, but why use the corncob on a DMR rifle? If they’re getting a new rig, get a new can that lends itself a little better to accuracy. Use that budget!

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My buddy just got his new Mk12 mod1 setup. I think it came out prettydamn nice. I promised him I’d post a picture.He was able to snatch the Leupold just in time!

And better glass. Glass technology has gotten so much nicer since the Mk 4 days. Something like a Mk 6 3-18, Any of the 1-8s from Trijicon, Leupold or Nightforce, etc… so many great options.

Also a redux of the 12th can made out of Ti would be kinda cool.

They usually are, but will go out from time to time. I really miss buying it from PSA. It was always $29 per 100.

This. And probably replacement parts availability. H&K can crank out parts far faster than Crane would be able to. Though they do kinda throw a wrench in the plans with all their proprietary stuff.

That is sharp. Tell him to join Arfcom and hang out with us in this thread lol.

The Mod H already proved a 16" could do most everything the Mod 1/0 ever did, and the ole TS30A2 is probably beans compared to the 3-18 in cost. Not to mention reordering things they already had vs the red tape of ordering new things and having to compete contracts, etc...

Brownells has blem A1's on sale.

Oh absolutely! Dear God, please give the Mod1 Redux an FFP MIL/MIL scope and the world shall rejoice. Hallelujah!

Did you have a chance to test the 5.56 and 223 wylde Ballistic Advantage barrels? Thoughts?

Decided to convert my Mod1 to a Mod 0 so I'm selling some good parts. Used FF RAS, Surplus Pelican 1700 with cutouts, AE flash hider and collar. My USMC surplus scope is listed on ebay with the NLS rings.

just like the mod 1 was a KAC baby, the mod H and dick swan/PRI/Holland, its not whats best for the operator....its whats best for HK and the govt contract. once you understand that, many things make sense....cough cough Beretta M9s not glocks, HK 416 not a heavy barrel Mk18, tire brand on vehicles, clothing brands.....etc.

if you shoot all your ammo at the end of the year, you get more allotted next year. doesnt matter if u shoot it burn it bury it or lose it. ;)

Listed my faux knurled AEM5 in the EE if anybody is looking for one to hold them over until the real thing arrives

So I'm building a Mod H. As I understand it the Noveske Recon barrel was original spec of the mod and I understand that it will need Smith work. What I don't understand is that I would think that it would require me to turn the barrel down and make the shoulder for the collar however the barrel OD is already smaller than the ID of the collar??

Any ideas or clarification on this that anyone has would be appreciated because I didn't buy a $400 barrel just to have one.....

Rest easy, you can just buy a Ballistic Advantage barrel already turned down specifically for the mod H for a fraction of the Noveske price.

I did consider that but my OCD got the best of me. In all seriousness though, how do they shoot comparatively?

Us cloners understand that all too well. I can't say anything about the Noveske barrels, as I've never really put any considerable amount of rounds through one. But the BA barrels I have all shoot lights out. Especially for the price point.

I believe they have a MOA guarantee, can't ask for much more for the money. I have a Douglas in my Mod 1 because of that OCD, but for everything that's any kind of a headache, I just take the easy way out and get a BA.

My SEAL Recce is a chopped down BA, and I'm very happy with it.

Well that's good to know and I appreciate it! Right now I'm still stuck on this Noveske and figuring out what's up with it but I think based on what you said I just may have to chop a BA and do the same for a Recce.

And I have a BA that I used for a build and it shot great so nice to know other contoured barrels of theirs shoot just as well!

The Noveske barrels that were used in the H were a special profile that is not available from Noveske. Unfortunately, the barrel you have (Noveske’s standard contour) cannot be reprofiled into the correct profile. You CAN have a competent gunsmith, such as ADCO, make a custom collar and profile that will work with the AEM5, but it won’t be quite right. They offered to do that for me when I purchased a barrel that I thought would work but was the wrong profile, but I ended up selling it and getting a Douglas. Not quite right for the Holland, but that’s fine. As others have said, the BA seems to be a phenomenal offering for the price. I have an 18” with OPS contour sitting in my shop for the Mod 0 I’m building for my wife.

The BA 18" SS SPR barrel with OPS contour can be had right now from Monmouth for $141 shipped.

Okay thanks so much for the info! So it seems that either way someone can't be clone correct to the exacting specs. So seems the decision is to determine which would be closer to clone correct, having a noveske barrel and a contoured collar or a Douglas,  BA, or CLE barrel with the correct collar? I may opt for the collar since I've already plunged into the Noveske barrel price.

Damn, hard to pass that up. Maybe I'm changing my mind and will see if I can return the Noveske.

Got the Mod1 out to 672 this weekend to ring in the new year on some steel IPSCs

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Awesome. The natural range out there tops anything we got around here.

You guys out west have it so good.

Right? Damn cornfields in the way out here.

Yea, I'm really fortunate.  Im originally form the east coast, but made the lifestyle change to prioritize outdoor adventure after the first 22 years of my life on the east coast and moved cold turkey out here after ETSing.  Figured that was a good a time as any.  I'm never going back east.  Shooting, camping, hiking, off-roading, etc. is exactly what I wanted and can't get enough of.

Couple more I just had to downsize since ARF restrict you to 3MB per pic now....  Added one with the gas .308 w the 12 peeking in the background.  that tripod is getting painted here STAT.

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If surfing wasn't a huge part of my life, I'd have moved out there years ago.

you guys in the corn states have some MONSTER freaking whitetails though.  I'd love to chase some of those around your state for a little while.  So you have some things going for you.

I hear you, brother.  I grew up an hour down I40 from Wilmington and Wrightsville Beach and our family summer vacations were always to Emerald Isle and Morehead City.  Got plenty of that too stationed in Hawaii.  Guess the mountains and desert just has more of a pull for me than the beach.  I do miss me some Cookout and Eastern NC BBQ.......

I'm not a hunter, so it really doesn't mean much to me.

Used to be stationed in CO and I absolutely loved it there. Had plans on going back there when I got out, but meeting the misses and that state going tarded screwed that up.

Fuck I'll take the corn fields! I got buildings in the way out here!

Never thought I would be able to say this, but what comes after MK12......

lol, small world; I live and work on Wrightsville Beach proper. It's 7-degrees down here this morning.

Stunning. Very jealous of the terrain.

I'm guessing you guys are having a winter like us in ID. Where the hell is the snow?

What's it under on ebay? Can't seem to find the scope you have listed?