7×7 Collars

The 7×7 Collars are a new take on an old Allen Engineering product. Formerly known as the M4 Collar, we renamed it to avoid confusion with the M4 suppressors which they are not compatible. The name “7×7″ comes from the step the collar sits on. The step is roughly .700″ past the shoulder and the diameter of the barrel between the shoulder and the step is also around .700”. This is an extremely common step among a variety of barrels which makes these collars a versatile option. 

The original M4 Collars were designed to fit barrels with a .745″ barrel diameter after the 7×7 step, but this caused a looser fitment with slightly smaller diameter barrels. So with the new 7×7 Collars we decided to offer them in a range of sizes so you can get a tight fitment. Starting at .725″, the collars go up in size every .005″ until .745″. These will also be available in both A-Mount and B-Mount configurations. 

To determine the correct collar sizing you should first verify that you have the correct 7×7 step on your barrel. With a set of calipers, measure the distance between the shoulder and the step. You should be getting around .700″. Now measure the diameter of your barrel between the shoulder and the step. You should be getting around .700″. If both of those measurements line up then you have the 7×7 step.

If you have the correct 7×7 step we can move on to determine the correct collar size. With your calipers, measure the diameter of your barrel after the 7×7 step on the side closest to the gasblock. Whatever size you measure order the matching collar. If you are between the .005″ sizing, round up to the larger size.