For those interested here's a very well written list for the various MK12's.
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 ¼ 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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Statistics: Posted by longrangehunter — Fri Jan 01, 2016 12:18 pm