Just some history from my own perspective.
I’ll just start from the get go. The MK12 SPR didn’t start as a rifle. It was an upper receiver group. SPR originally stood for “Special Purpose Receiver”. It wasn’t called a mK12 either as I recall. It was issued (as how we got them) with the Upper Receiver Group (URG), A scope, (varied depending on customer), Harris Bipod, 3 20 rd magazines, and an Ops Inc Model 12 suppressor. It came in a light brown pebbled case with combo locks.
It was supposed to be an accessory kit for M4 so a team could have precision capability without a whole new gun. If you look for pictures of 1st SFG in the Philippines from 2002-2004, you’ll see them on an M4 lower. Some people think this was a rifle modified with an M4 stock but it’s just the SPR on an M4 Lower.
That changed a little later when an entire rifle was desired. Hence, MK12 SPR (Rifle replaced Receiver). What they added was an M16A1 lower receiver with an M16A1 buttstock (shorter than an A2 and better IMO), A Knight’s Armament (KAC) 2 stage adjustable full auto trigger, a KAC ambidextrous selector, and a leather sling. The scope was either a Nightforce 2.5-10x or a Leopold 3-9x. Navy likes NFO and Army likes Leupold. They used M16A1 lowers mainly because they have thousands of them, whereas the M4A1s were limited to Operators. Note: The Army still had M16A2s and were still using burst. They didn’t go M4A1s for awhile.
There are three versions of the MK12 SPR. The MK12 Mod 0, MK12 Mod1, and MK12 Mod H. The Mod 0 and 1 were NSWC Crane built guns and the Mod H was a recce version made for 5th SFG at 5th SFG.
Here’s a list of what’s on the Mod 0 and Mod1:
The Lowers stayed the same.
Mod 0 – Douglas 1-8 18” rifle gas bbl, Ops Inc Brake and collar (these and the Suppressors were made by Allen Engineering in CA), PRI folding front sight/gas block, PRI round free float handguard Gen1/2, ARMS PEQ rail, ARMS 40L rear sight, Colt or whatever upper receiver they used (usually Colt) provided by Crane, Colt rebuilt BCG, PRI Gasbuster CH, Arms #22 QD rings (Med Height), Harris bipod both short and mediums (I’ve seen Arms and KAC bipod adapters). Ops Inc Model 12 Suppressor, and either an NFO or Leupold scope. Depending on the kit ordered by the unit, it might come with a PVS22 NVD.
Mod1 – – Douglas 1-8 18” rifle gas bbl, Ops Inc Brake and collar, Badger Low profile Gas block, KAC Medium length Free Float Quad rail, KAC folding front sight, KAC folding rear sight (either the 300m peep or mostly, the 600m adjustable), Colt or whatever upper receiver they used (usually Colt), Colt rebuilt BCG, PRI Gasbuster CH, Arms #22 QD rings (High), Harris bipod both short and mediums (KAC Adapter), Ops Inc Model 12 Suppressor, and either an NFO or Leupold scope (2.5-x24 NFO; 3-9x36 Leupold TS30, later 2.5-8x36-USMC). We’d use whatever we wanted though, usually leftover 3.5-10x Leupolds. Depending on the kit ordered by the unit, it might come with a PVS22 NVD.
With the Mod1, around 2010, we changed out the KAC triggers with Geissele 2 stage full auto triggers. FWIW, the KAC triggers were junk. The engagement surfaces would burr up and the triggers would fail. They were adjustable too so any nug with an allen wrench could F up a trigger. This was the only change to the lowers. Mod 1s also got equipped with a black Ergo grip.
The MK12 was required to have full auto in case it had to be used as a combat rifle in lieu of an M4 or M16.
The buttstock was an M16A1, usually the trapdoor version. The M16A1 stock was preferred because it's shorter and better for optics.
MK262 77gr was developed specifically for this gun - which is the greatest 5.56 ammo ever developed, IMO.
I’ll just start from the get go. The MK12 SPR didn’t start as a rifle. It was an upper receiver group. SPR originally stood for “Special Purpose Receiver”. It wasn’t called a mK12 either as I recall. It was issued (as how we got them) with the Upper Receiver Group (URG), A scope, (varied depending on customer), Harris Bipod, 3 20 rd magazines, and an Ops Inc Model 12 suppressor. It came in a light brown pebbled case with combo locks.
It was supposed to be an accessory kit for M4 so a team could have precision capability without a whole new gun. If you look for pictures of 1st SFG in the Philippines from 2002-2004, you’ll see them on an M4 lower. Some people think this was a rifle modified with an M4 stock but it’s just the SPR on an M4 Lower.
That changed a little later when an entire rifle was desired. Hence, MK12 SPR (Rifle replaced Receiver). What they added was an M16A1 lower receiver with an M16A1 buttstock (shorter than an A2 and better IMO), A Knight’s Armament (KAC) 2 stage adjustable full auto trigger, a KAC ambidextrous selector, and a leather sling. The scope was either a Nightforce 2.5-10x or a Leopold 3-9x. Navy likes NFO and Army likes Leupold. They used M16A1 lowers mainly because they have thousands of them, whereas the M4A1s were limited to Operators. Note: The Army still had M16A2s and were still using burst. They didn’t go M4A1s for awhile.
There are three versions of the MK12 SPR. The MK12 Mod 0, MK12 Mod1, and MK12 Mod H. The Mod 0 and 1 were NSWC Crane built guns and the Mod H was a recce version made for 5th SFG at 5th SFG.
Here’s a list of what’s on the Mod 0 and Mod1:
The Lowers stayed the same.
Mod 0 – Douglas 1-8 18” rifle gas bbl, Ops Inc Brake and collar (these and the Suppressors were made by Allen Engineering in CA), PRI folding front sight/gas block, PRI round free float handguard Gen1/2, ARMS PEQ rail, ARMS 40L rear sight, Colt or whatever upper receiver they used (usually Colt) provided by Crane, Colt rebuilt BCG, PRI Gasbuster CH, Arms #22 QD rings (Med Height), Harris bipod both short and mediums (I’ve seen Arms and KAC bipod adapters). Ops Inc Model 12 Suppressor, and either an NFO or Leupold scope. Depending on the kit ordered by the unit, it might come with a PVS22 NVD.
Mod1 – – Douglas 1-8 18” rifle gas bbl, Ops Inc Brake and collar, Badger Low profile Gas block, KAC Medium length Free Float Quad rail, KAC folding front sight, KAC folding rear sight (either the 300m peep or mostly, the 600m adjustable), Colt or whatever upper receiver they used (usually Colt), Colt rebuilt BCG, PRI Gasbuster CH, Arms #22 QD rings (High), Harris bipod both short and mediums (KAC Adapter), Ops Inc Model 12 Suppressor, and either an NFO or Leupold scope (2.5-x24 NFO; 3-9x36 Leupold TS30, later 2.5-8x36-USMC). We’d use whatever we wanted though, usually leftover 3.5-10x Leupolds. Depending on the kit ordered by the unit, it might come with a PVS22 NVD.
With the Mod1, around 2010, we changed out the KAC triggers with Geissele 2 stage full auto triggers. FWIW, the KAC triggers were junk. The engagement surfaces would burr up and the triggers would fail. They were adjustable too so any nug with an allen wrench could F up a trigger. This was the only change to the lowers. Mod 1s also got equipped with a black Ergo grip.
The MK12 was required to have full auto in case it had to be used as a combat rifle in lieu of an M4 or M16.
The buttstock was an M16A1, usually the trapdoor version. The M16A1 stock was preferred because it's shorter and better for optics.
MK262 77gr was developed specifically for this gun - which is the greatest 5.56 ammo ever developed, IMO.
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