Special Purpose Rifle (SPR) Mk12 mod1 Replica w/ Pro-Win Gearbox Install!

[ILLusion]

I've had this project rifle in the works for a while now and externally, it's been completed for a while. Only very recently have the internals been completed to make this gun... "leet" to match its real steel version.

The basis for this rifle, as was with my NSW DEVGRU CQB-R project, is to get it as close to an accurate replica of its real steel counterpart as if it were to come direct from factory or as issued to the operator. All accessories, add-ons and features are all to closely mimic as possible how the gun would be received in real steel form.




About the rifle platform (paraphrased from http://en.wikipedia.org/wiki/United_...urpose_Rifle):


United States Navy Mark 12 Mod 1 Special Purpose Rifle


mod1 as employed by NAVSPECWAR (Naval Special Warfare) operators

The United States Navy Mark 12 Mod 1 Special Purpose Rifle (SPR) is a rifle that has been in service with the United States special forces in Operation Enduring Freedom and Operation Iraqi Freedom. SPR initially stood for Special Purpose Receiver, but that nomenclature seems to have disappeared as the weapon became a stand alone weapon system, and not just an add on upper as part of proposed SOPMOD upgrades. SPR now means Special Purpose Rifle. It was eventually type classified by the Navy as the Mk 12, though the Army also uses this designation.


Background

This weapon system, used by Special Forces units of both the US Army and US Navy, is a heavily modified deviation from the familiar AR15/M16 line of infantry weapons, and thus is chambered for NATO standard 5.56 x 45 mm caliber ammunition. It serves a light sniper/designated marksman role. The SPR was originally proposed by Mark Westrom, currently president of Armalite, while at the Rock Island Arsenal. The SPR program was an outgrowth of the desire by both US Army and Navy special forces for a rifle with greater effective range than an M4 type Carbine but still shorter in length than a standard issue M16A2/A4. The SPR program appears to have grown out of both the SOPMOD Block II program, and the US Navy SEALs 'Recon Rifle' (a 16" flat-topped AR-15/M16 Carbine). The Naval Surface Warfare Center, Crane Division (often referred to as NSWC-Crane or just Crane) essentially expanded on the Recon Rifle, an idea that some SEALs maintain was a waste of energy and money.

The exact history of the Mk 12 is still something under debate, but its become apparent that there are between four and five prime iterations of the weapon, culminating in the last Mk 12 Mod 1 version. One progression has four models: SPR Proto 1, SPR Proto 2, Mk 12 Mod 0 and Mk 12 Mod 1. The other progression is: SPR, SPR/A, SPR/B, Mk 12 Mod 0, and Mk 12 Mod 1 (all as separate iterations). The specifications entered will follow the second progression.

There is also increasing agreement among observers and small-arms historians that different US military service branches deploy different iterations of the SPR. Available evidence, including both US DOD photographs and privately-obtained photographs (like the ones shown below), consistently show US Army SOF units using the Mk 12 Mod 0 iteration of the SPR, while NAVSPECWAR operators have been identified as using the Mk 12 Mod 1 version.

Though the Mark 12 Mod 0 Special Purpose Rifle had enjoyed relative obscurity for most of its short life, recently it has been featured prominently both in media photos of the Iraq conflict and in interactive video games such as the government-created title America's Army: Special Forces, the console title Tom Clancy's Ghost Recon 2, and the freeware first-person shooter True Combat: Elite. In a civilian capacity, copies (commonly called "SPR clones") of the SPR rifle have also become quite popular among shooters and collectors in the US, with several reputable builders of AR15-style rifles making civilian-legal copies of this very accurate rifle.


Specifications
* Upper Receiver: The upper receiver blocks themselves were initially supplied by Colt, with some of those being from Diemaco as well (Colt has been outsourcing parts of its production to the Canadian firm for a while now—Colt purchased Diemaco in February 2005, but continues to supply firearms under both names). There is a debate about whether the upper blocks for the Mk 12 rifles, though, came solely from Armalite, or were a mix of receivers from Armalite and Colt/Diemaco. All of these upper receivers were flat top, but have been seen both with the old style tear drop forward assist and the new round style. There is, however, no obvious consistency in this regard.
This airsoft replica uses a Colt branded receiver, manufactured by G&P as their "SPR Metal Receiver Kit" and comes with the ergonomic SPR pistol grip as well. Some features on this receiver make it a closer replica to real steel than any other metal receiver for standard AEGs. This receiver kit also includes the Knight's Armament big cocking handle lever and the forward assist knob is of the round variety.

* Lower Receiver: When the SPR program was still in the phase where it was just a receiver, Crane assembled all of its prototypes using either M16A1 or M4A1 lowers. It is unknown whether this pattern continued as the program progressed. There is also some issue about whether, when the Navy type-classified the weapon, Precision Reflex Incorporated (PRI) began assembling the rifles themselves. While a number of options were tried in the end, a Knight's Armament Company (KAC) 2-stage trigger was finally decided upon as the standard fit.

* Handguards: In all cases a free floating forearm is utilized. This handguard does not ever touch the barrel, increasing the accuracy of the weapon by removing increased vibration exerted on the barrel by the rest of the gun. The first SPRs use a PRI Gen I or Gen II carbon-fiber free-float tubes. The SPR/A, SPR/B, and Mk 12 Mod 1 all use the Knights Armament Company (KAC) M4 Match Free-Floating RAS (Rail Adapter System). The Mk 12 Mod 0 uses PRI Gen III free-float tubes. The Gen I and Gen II Freefloat Forearms are combined with the Atlantic Research Marketing Systems (ARMS) #38 SPR MOD Sleeve, while the Gen III Freefloat Forearm, due its it larger barrel nut, only works with the ARMS #38 SPR PEQ-2-3.
This airsoft replica uses a G&P free floating rail forearm, closely replicating the Knight's Armament design. Along the shooter's right side of the forearm, it bears the markings: M-4 SNIPER R.A.S. - PN: 99167. Along the shooter's left side of the forearm, it bears the markings: ARMAMENT CO. VERO BEACH , FL. (561) 562-5697

* Barrel: A 18 in (457 mm) threaded-muzzle match-grade free floating stainless steel heavy barrel with a 1:7 in (178 mm) rifle twist ratio. The barrels have a special contour to maximize accuracy and minimize weight; they are manufactured by Douglas Barrels. An OPS Inc. muzzle brake and collar (to align the OPS Inc. 12th Model Suppressor) is installed with the barrel. These barrels were designed to take advantage of the new Mk 262 cartridge, which uses a 77 grain (5 g) bullet, that is now being fielded.
This airsoft replica uses a GB-Tech free floating outer barrel, closely replicating the Knight's Armament design. The muzzle brake featured on it is a replica of the OPS Inc. muzzle brake.

* Buttstock: SPRs in action have been seen with M16A1 buttstocks, M16A2 buttstocks, retractable M4 buttstocks, and the Crane Enhanced retractable buttstock. It is readily compatible with any type of stock system developed for the AR-15 weapon system.
This airsoft replica uses a 3-position G&P replica of the NSW Crane stock and houses a 9.6v 2200mAh battery pack.

* Sights: The original SPR used an early PRI flip-up front sight with an elevation dial, which has since been discontinued. The Mk 12 Mod 0 uses the current PRI flip-up front sight. The SPR/A, SPR/B, and Mk 12 Mod 1 use the KAC rail foreend flip-up front sight. The SPR and Mk 12 Mod 0 use the ARMS #40 flip up rear sight. The rest of the models use the KAC 600 meter flip up rear.
This airsoft replica uses the GB-Tech replicas of the KAC rail foreend flip-up front sight and the KAC 600m flip up rear sight.

* Optics: Due to the relative modularity of the system, optics (as well as almost everything else) can be mounted per the operator's wishes, however, this weapon system is most often seen with a 3.5–10×40 mm Leupold LR M3 (SPR/A), a 2.5–9×36 mm TS-30 (SPR/B), or a 3–9×36 mm TS-30 A2 (Mk 12 Mod 0/1) Mid Range/Tactical Illuminated Reticle Dayscope (civilian versions are known as the Leupold Mark 4 MR/T 3–9×36). Night vision devices can also be attached. These scopes usually come with flip open dust covers and a honeycomb anti-glare anti-reflection device (ARD).
This airsoft replica uses the G&P replica of the Leupold M3 and has a 3.5-10x optical zoom level magnification.

* Mounts: As mentioned before, a long accessory rail, called a SWAN Sleeve (ARMS SPR MOD or ARMS #38 SPR PEQ-2-3), manufactured by ARMS, is installed, running the length of the rifle. The SPR/A and SPR/B both used the KAC M4 Match FF RAS. Two ARMS #22 Throwlever 30 mm steel rings are used to mount the dayscope. The SPR/A, SPR/B, and Mk 12 Mod 1 use ARMS #22 high rings, while due to the increased height from the SWAN Sleeve, the SPR and Mk 12 Mod 1 use ARMS #22 medium rings. An under-the-handguard ARMS #32 Throwlever mount is used to mount the Harris bipod (the ARMS #42 Throwlever mount is used to mount the Versa-Pod); this features a quick release action.
This airsoft replica uses a GB-Tech replica of the KAC 30mm high mount rings.

* Bipod: Originally Versa-Pods, a cheaper Chinese-made copy of the relatively expensive Parker-Hale swivel bipod, were used, but were taken off the system after the initial SPR. Currently, a Harris swivel model bipod is typically used with the SPR, and is sometimes seen with a KMW Pod-Loc tension adjustment device. As mentioned above, the bipod is mounted via a ARMS #32 throwlever device attached to the bottom rail of the rifle's forearm. The ARMS mount is used on both Mod 0 and Mod 1.
This airsoft replica uses a Harris swivel bipod and attached via a King Arms replica of the ARMS #32 thorwlever mount.

* Suppressor: The suppressor threads directly onto the OPS Inc. muzzle brake and uses the collar to stay centered. It is an OPS Inc. 12th Model SPR Muzzle Brake Suppressor (MBS).
This airsoft replica uses a GB-Tech replica of the OPS Inc. 12th Model SPR Muzzle Brake Suppressor (MBS) and it does a decent job at hiding an extended inner barrel as well as muffling the sound signature of the shot.

* Ammunition: The SPR is not used to fire standard issue M855 ball or M856 tracer (and even less so M193 ball). Due to the limits in performance and poor accuracy of the 62 grain (4 g) M855 ball (standard NATO green-tip .223), the Mark 262 Open Tip Match (OTM) round was developed as a more accurate 5.56 × 45 mm round. The cartridges are made by Black Hills Ammunition. The first production batches were designated the Mk 262 Mod 0 and used a Sierra Bullets MatchKing 77 grain (5 g) Hollow Point Boat Tail (HPBT) bullet without a cannelure (crimping groove). Black Hills then approached Nosler, who made a similar 77gr OTM bullet, and Nosler agreed to supply cannelured bullets to Black Hills. This load was designated Mk 262 Mod 1. Recently, Sierra agreed to add a minimal crimp to their bullet, and this has since replaced the Nosler bullet in the current versions of Mk 262 Mod 1.
This airsoft replica takes a healthy dose of 6mm Guarder 0.28g BBs.






The internals used are:
- PGC (Pro-Win) 7mm custom gearbox, featuring a spring release lever, split gearbox design, CNC construction, quick spring swap feature. and a one piece hop up/gearbox/cylinderhead design for best possible seal.
- PGC M130 spring (allows the gun to hit a consistent 400fps)
- PGC tappet plate
- Eagle Force Hummer 1100L motor
- Prometheus Motor Gold Pin
- Prometheus low resistance silicone wiring running uninterrupted to the stock
- Prometheus double torque gear set
- Prometheus anti-reversal latch
- Prometheus 7mm ball bearing bushings
- Prometheus HARD piston (custom fit)
- Prometheus v2 spring guide
- Prometheus 7mm enhanced selector plate
- Prometheus 6.03mm 590mm tightbore inner barrel
- Big-Out H-Hop Hop Up Bucking (black)
- Systema bore up cylinder kit
- King Arms Gear Sector Clip

[Hades]

Very nice Brian. I been looking at doing somthing similiar after I get my M-14 EBR project outta the way.

jesus dude. everything in there is top of the line. Next time you have it apart, get a pic of the split mechbox. thats hawt

video of it firing too, like to see the eagle force in action.

[roberto]

I am a big fan of the SPR and that looks great. Must be solid as a rock too

Rob

[bruce]

Very nice Brian. Like Droc mention, would like to hear more about the Pro-Win split mechbox design. Any thoughts on the durability of making a 450fps out of it?

[ILLusion]

I think you could easily get that gearbox up to 700fps with a hard recoil kit and not worry about damage!

hmm... hard recoil kit...

[Kuraitenshi]

really niice

[thePiRaTE!!]

Looks great! I was thinking of trying the PGC myself. How much effort and expertise did you employ to get it tight with your build? Are PGC tweaking their mech box as they go, or do they all have that 'anodized not accounted for in measurement' thing?

How does that build sound?

Once again, nice job.

[ILLusion]

I seriously do NOT recommend the PGC gearbox for anybody who fears lots of modifications.

Generally, MOST of the modifications had to be done to the metal receiver. My job would have been made SO MUCH EASIER if I had a mill... but I don't. I ended up using my trusty Dremel tool and a Tungsten Carbide cutting bit.

Depending on the metal receiver you use, you may have to do a lot of mods, or very little. The PGC gearbox comes with a media CD that contains pictures of what needs to be modded for various receiver manufacturers. Included are Hurricane, G&P v1, G&P v2, and Guarder.

Handiest tools for the install (if you don't have a mill):
1. Dremel
2. Calipers
3. Files

The piston that comes with the kit is crap and I killed it in less than 200 shots while just testing at home. Cracked in a couple of places. Piece of garbage. The sizing tolerances of the gearbox are also a bit off, so not every piston will drop right in without modifications. I ended up modifying a Prometheus Hard piston to get it to fit.

Don't listen to earlier reports of PGC not accounting anodizing thickness in to their measurements. They did. When you deal with products that have extremely tight tolerances, expect the parts to be tight! (tight is good... mmm...) If pieces go together very easily, then that means tolerances are loose. This is why AKs always work and Armalites jam easily.

In this case, tight tolerances are good as it's noticed when fitting all the pieces of the shell together. You wouldn't want that shell to be flexible when all assembled, would you?

Overall, the gearbox is very very solid. I'm liking it very much.

[thePiRaTE!!]

Thx for that. Was the motor a special choice, or personal preference? How does it sound and perform vs the EG-1000?

Admittedly, my project my never get off the ground. As you may have seen, my 'primary' is an M-4 MRP using the 'Bestgun' kit. It has its own proprietary hop-up. I haven't yet bothered to determine if the PGC could actually work with my gun.

[ILLusion]

I bought the motor just to play around with it and see if it really made a difference... on a gun that can already handle a large battery pack fine, it made no noticeable difference, although I'm sure it helped reduce current draw. On a gun using a mini pack, the difference is more noticeable, but both ROF as well as torque went up compared to an EG1000. It sounds the same to me. If anything, slightly louder, since its ball bearings translate sound vibration moreso than the bushings of the EG-1000.

I don't see why the PGC wouldn't fit your MRP. I'm sure you can get it to fit, you'll just have to make some further modifications to your receiver, such as clearing out the hop up/feeding area.

Break out the dremel!!!

[Dr_Tinshnipz]

How much did this cost you?!

[Xenos-Fear]

Originally Posted by Dr_Tinshnipz

How much did this cost you?!

Not sure he wants to remember that ! LOL

Very nice piece Illusion ! Always great to see your master creation ! Good work !

[ILLusion]

Originally Posted by Dr_Tinshnipz

How much did this cost you?!

Almost all of the parts can be found on Wargamer's site. You should be able to get a general idea from those numbers.

[Guardian]

Good god man that is spectacular! A very big “Tip of the Hat”.
When can we see this baby in action Brian?