The Mark 12 Special Purpose Rifle (SPR) is a designated marksman rifle (DMR) developed by the Naval Surface Warfare Center Crane Division for SOCOM units. In the past, the United States Special Operations Forces used the Mk 12 SPR in Operation Enduring Freedom and in Operation Iraqi Freedom.
There are several airsoft version of the Mk 12 SPR on the market. However, none of them matches the real photo above exactly. In this article, we will attempt to build a replica DMR that closely resembles the actual firearm (shown in the photo above) using existing off-the-shelf parts.
The base airsoft gun to use for this project, is obviously the M4 carbine, because that's what the real Mk 12 SPR is based on. With an airsoft M4 carbine, the biggest conversion is to change the quad rail system to match the Mk 12 SPR. There are several off-the-shelf options. We will examine each one in detail below.
The A&K 440 FPS Full Metal M16 SPR Mod 0 Airsoft Electric Gun AEG almost matches the Mk 12 SPR we want to build exactly. Therefore it is an excellent base to start.
If you look closely at this gun, you'll see that it has the wrong magazine and has the fixed shoulder stock rather than the crane collapsible stock. Also, the foregrip has to go. But it is relatively easy to convert this gun into the one we want to build. Simply replace these discrepancies with the correct parts we'll outline below. Just that where the handguard meets the receiver is a little different than the real thing.
The best base to use for this project seems to be the Umarex Elite Force M4 CQB AEG Airsoft Rifle, Black. If you look at the photo above closely, you'd see that the Elite Force M4 CQB has handguard and rails closely resembling the Mk 12 SPR. The rails on the sides and bottom are screwed on and should be replaceable with shorter ones to match the Mk 12 SPR. The Elite Force M4 CQB already comes with the crane shoulder stock and the M4 receiver that matches the Mk 12 SPR, so very little conversion work needs to be done in those areas.
Note that we purposely used the tan version in the photo above, to help you clearly see the parts. Obviously, you'd want to use the black version to match the Mk 12 SPR. The black version is identical to the tanned version, except for the color. Photo of the black version is shown below.
Keep in mind that the handguard in the Elite Force M4 CQB is a bit shorter than the Mk 12 SPR handguard. In addition, the Elite Force M4 CQB is made out of nylon polymer (plastic). So this route is a good path if you want a lighter Mk 12 SPR or if you want to use it in a CQB field.
We counted the number of indents on the short Picatinny weaver rails of the Mk 12 SPR. There are seven indents. We could not find the exact short rail, but here are some options:
The Magpul L2 MOE Rail Section, Black closely resembles the rail seen on the Mk 12 SPR. It only has five indents, but is more than enough to mount your accessories. Three of these would make your replica look like the real thing.
Not exact replicas, the M4 M16 AR15 Handguard Weaver Rail Set provides close proximity to the real thing in function. It has seven indents, just like the rails on the Mk 12 SPR, so it will function the same. Only the mount location causes these rails to be slightly longer. But still excellent option for this build.
The sniper rifles and DMR's, based on the M16, use shorter M16 magazines used during Vietnam war. The short magazines allow the soldier to go prone with the rifle on bi-pod. The standard M4 carbine comes with longer magazines that needs to be replace for this build. The DBoys Airsoft 70rd M4 / M16-VN Metal Mid-Cap Magazine -For AGM, CA, DBoys, Echo 1, G&G, ICS, JG, KWA, and SRC M4/M16 AEGs serves this purpose well.
The Mk 12 SPR generally has the Leupold Mark 4 LR/T 3.5-10x40mm (30mm) M3 Illum. TMR installed on top. If you are building an exact replica, then this is a great scope to use. But its 10x magnification and its hefty price tag are too much for airsoft purpose.
Instead, we suggest the Nikon ProStaff Rimfire 4 x 32 Black Matte Riflescope (Nikoplex). It looks very similar to the Leupold and still provides 4x magnification that is truly useful on an airsoft field. The cost is also much more affordable than the Leupold.
The real Mk 12 SPR uses the Harris Engineering S-BR Hinged Base 6 - 9-Inch BiPod. It's available to civilians and will work on your airsoft gun. But you'll have to get an Picatinny weaver adapter for it, or find another way to mount it to your airsoft handguard.
The Precision Grade Bipod fullsize 3 Adapters looks very much like the bipod on the Mk 12 SPR. It is also far more inexpensive compared to the Harris bipod above. More importantly, it comes with Picatinny weaver adapter to mount easily to your replica. We suggest going with this bipod unless you need authenticity.
Front sight is not really needed on this replica, because you will have a scope on it. But to match the real thing, you should get the PRI Flip up Front Sight.625 Diameter / with Gas Block. This front iron sight matches the Mk 12 SPR photo above exactly and is used on Mk 12 SPR Mod 0. This front sight could come in handy if your scope ever fails.
JG has cloned the Mk 12 SPR front sight and market it as the SPR Type M4 M16 Full Metal Flip Up Front Sight for Airsoft Rifles. It's a very inexpensive alternative to the real thing above. And it is quite sufficient on an airsoft gun.
Much like the front sight, if you are going to put a scope on the Mk 12 SPR replica, then you won't really need the rear sight. The iron sight does come in handy if your scope fails, or if you just want to build an exact replica. The Kac 600M Micro Flip Rear Sight Blk is used on the real Mk 12 SPR. Since it mounts via the Picatinny weaver rail, you can use this iron sight on your airsoft gun as well.
The Airsoft M4 614 Retractable Crane Stock w/ Rubber Shoulder Pad looks identical to the collapsible shoulder stock on the Mk 12 SPR. It is made by JG. Unfortunately, it doesn't come with the buffer tube, but the one below will work.
A buffer tube will help you attach the collapsible shoulder stock to the SPR replica. Any M4 buffer tube will do. This Airsoft Lightweight Aluminum Replacement M4 CQB Buffer Tube for Crane Stocks - JG M4 CQB F6624 OEM is compatible with the JG shoulder stock above.