Allen Engineering SPR Collar

The SPR collar is the traditional collar system for Mk12s. They have an internal step that interfaces with a step in Mk12 barrels that prevents rearward movement. The set screw, typically positioned on the bottom prevents rotation. Here are the different SPR collar options:

Mod 1 – This was designed for use on Mk12 Mod 1 and Mod H rifles and will work on any properly profiled Mk12 barrel.

Mod 0 – This was designed for use on the Mk12 Mod 0. This will work on any properly profiled Mk12 barrel. It functions the same as the SPR Long collar but is shorter to prevent interfering with the Mod 0 FSB.

B-Mount – This was designed to convert your Mk12 barrel to accept B-Mount suppressors (AEM2, AEM3, and AEM4). This will work on any properly profiled Mk12 barrel.