Talk:Mk 12 Special Purpose Rifle

SPR vs Mk 12 Mod 0

The SPR used the PRI Gen I and Gen II Freefloat tube. The Gen I Freefloat Forearm has no vent holes. On a Gen II Freefloat Forearm, the teeth of the barrel nut are visible. The barrel nut and collar assembly is the same diameter as the forearm. On the main page, all of the SPRs with PRI forearms pictured have Gen II forearms.

The Mk 12 Mod 0 uses the PRI Gen III Freefloat tube. A Gen III Freefloat Forearm has an oversized barrel nut, that is larger in diameter than the forearm itself. This requires notches cut out in the ARMS #38 sleeve.Pettifogger 21:49, 21 Oct 2004 (UTC)

From all the photos I have seen, they've all used Gen IIs (the Mod 0s)? I'm not sure I understand. -Tin

All the pictures are of the older SPRs. They have the Gen II free-float tube and the older PRI flip-up front sight with elevation dial. This discussion on AR15.com has a detailed list on the SPR variations.Pettifogger 18:35, 11 Nov 2004 (UTC)

SPR series progression

I assume the idea of two disputable series of evolution comes from Christopher Bartocci's Black Rifle II. He does not use the term "Proto I" and "Proto II", but does refer to a first-generation and a second-generation. The first-generation of SPRs had aluminum free-floating handguards and Swan #38 sleeves and were meant for M4A1 lower receivers, so they are probably the prototype upper receivers seen on page 107 and 108. The caption on page 108 refers to a "second variation of the SPR upper receiver", which I assume to mean the second of the three pictured on page 107.

I am convinced that the second-generation of SPRs refers to the SPR, SPR/A, and SPR/B. The second-generation used M16A1 lowers and SPRs, SPR/As, and SPR/Bs are seen with M16A1 lower receivers. There was a 100-unit production run of the second-generation SPR, and most of those were sent to Southwest Asia for Operation Enduring Freedom. There are numerous images of SPRs, SPR/As, and SPR/Bs in use in Afghanistan, so it is highly probable that SPRs, SPR/As and SPR/Bs are the second-generation SPRs.

It should also be noted that the Mk 12 Mod 1 is an alternative to the Mk 12 Mod 0, not a replacement. Both are currently in use. Pettifogger 22:24, 21 Oct 2004 (UTC)

Mk 262 Mod 0

Are we really certain about the use of Hornady 75gr bullets in the original Mk 262 Mod 0 load? It is my understanding from several sources that the Mk 262 Mod 0 used the Sierra 77gr MatchKing exclusively.

The information about Hornady 75 gr bullets came from an old version of the Ammo Oracle website. This presumably was based on previous SOCOM usage of Hornady 75 gr bullets.Pettifogger 23:43, 11 Jan 2005 (UTC)

The following is from The Ammo Oracle websited dated 21 May 2004.

Q. What about Mk252 or Mk262 Mod1?

Due to the poor performance of M855 ammunition, particularly in short-barreled carbines of 10.5-14.5" in length, Navy SEALs, and eventually other SOCOM units, began experimenting with using loads originally designed for marksmanship units for combat. It was soon discovered that while these loads were both very accurate and had excellent terminal ballistics even from short barrels, the loads weren't quiet ideal for combat. The target bullets had no cannelure, and the bullets weren't crimped in place, which could allow bullet set-back during feeding and raise chamber pressures to dangerous levels. Further, most loads were of somewhat mild velocities, as the load was chosen with accuracy, not terminal ballistics, in mind.

Black Hills Ammunition was approached to make a slightly modified version of these loads for combat use. A cannelure was specified, the bullets were to be crimped, and the load was to be up to military chamber pressures, with maximum safe velocity being desired. The priemrs were to be crimped and sealed, and of coruse, overall length had to allow for loading in standard magazines.

The first load was given the Naval designation Mk262 Mod0. It contained a specially canellured Hornady 75gr "open-tip match" (a politically correct way of saying JHP) round, as used in Hornady's 75gr TAP load.

Black Hills had originally suggested Sierra's 77gr OTM bullet due to its reputation for accuracy, but Sierra was then unwilling to add cannelures to their bullets. Black Hills approached Nosler, who made a similar 77gr OTM bullet, and Nosler agreed to supply cannelured bullets to Black Hills. This load was designated Mk262 Mod1.

Recently, Sierra agreed to add a minimal crimp to their bullet, and this has since replaced the Nosler bullet in the current versions of Mk262 Mod1. As of April 2004, Mk262 Mod1 has seen extensive use in Affghanistan and Iraq, in carbines with barrels as short as 10.5", and has proven to be very effective at ranges that M855 is woefully inadequate from the same weapons. It is also commonly used in the Army's "Special Purpose Rifles" (SPRs), which are accurized 18"-barreled rifles used by soldiers with additional combat marksmanship training in a squad sharpshooter role.

Pettifogger 08:15, 27 Jan 2005 (UTC)

"Mod X" in article name

Could we possibly rename this article to simply remove the "Mod" portion of the designation in the title rather than have "Mod X." It seems cleaner in my mind than its current form. Any thoughts? -- Thatguy96 13:46, 20 July 2007 (UTC)

That to me seems equivalent to renaming the 5.56x45mm NATO page to "5.56 NATO", which was discussed and decided against. Spartan198 (talk) 13:23, 9 March 2010 (UTC)

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External links modified (February 2018)

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MK12 Accessories, specifically suppressors

Hi, I made some changes to the accessories section, specifically the area about the suppressors on the MK12. To be aware of a conflict of interest, I am part owner of Otter Creek Labs.

It seems unfair and incorrect to only mention the AEM5 and OCM5 by name when there are actually many different "clones" of the ops inc suppressor. In my changes, I have included a citation that compares 3 of them, in addition to the original. The AEM5 and Ops inc models definitely deserve a mention because they are the original, however anything else is just a clone and should either be referenced all together or not at all. Spacecrocs (talk) 18:58, 12 December 2021 (UTC)