From the Vault: Keith's Mk 12 SPR Clones

Let's go down the rabbit hole - actually a rabbit warren! - of the Mk 12 Special Purpose Rifle (SPR) used by United States Special Operations Forces. Brownells Gun Tech™ Keith Ford geeks out on the details of the Mk 12 Mod 0 and Mod 1 while he shows us his clones of these rifles. The Mk 12 Mod 0 was developed by the Naval Surface Warfare Center Crane Division to fill the gap between the M4 carbine and the 7.62 NATO chambered Mk 11 and M110 rifles based on the SR-25. The project started in 2000 with the development of an accurized, accessorized Special Purpose Receiver (upper) that could be dropped onto a standard M4 or M16 lower.

Mod 0 SPR upgrades include an 18" Douglas barrel with an OPS Inc. muzzle brake / suppressor mount, Sierra Precision pistol grip, and A.R.M.S. #40-L flip-up rear sight and QD scope mount. The handguard, gas block with flip-up front sight, and the Gas Buster charging handle all came from Precision Reflex Inc. (PRI). Original Mod 0s were built on old M16A1 lower receivers upgraded with a Knight's Armament two-stage competition trigger. The SPR will work with a mil-spec trigger, but the Knight's trigger is really needed for it to perform at its full potential.

Once Mk 12 Mod 0 rifles entered service, changes and upgrades ensued, leading to the Mk 12 Mod 1. The Mod 1 has a handguard, flip-up front sight, and 600-meter rear sight form Knight's Armament. It has a special Crane gas block, old-school M16A1 fixed stock, and various pistol grips. As soon as Mod 1s landed in the hands of individual operators, components were swapped out and changed. The Mod H is a Mod 0 with a 16" barrel and different gas block, plus a Double Star Ace SOCOM collapsible stock, which many operators quickly replaced with a Magpul stock.

All Mk 12 barrels have a 1-7" twist and are designed for Mk 262 Mod 1 ammunition with a 77 grain bullet that gives the Mk 12 an accurate, repeatable reach out to 850 yards. Operators who have carried a Mk 12 include Marcus Luttrell of "Lone Survivor" fame and his fellow Navy SEAL Jack Carr, author of "The Terminal List".


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