The Suppressor Alignment Gage (SAG) is a precision gauge used to verify the alignment of a suppressor to the bore of a firearm barrel. The Alignment Gauge is marketed jointly by Surefire and by Geissele.
It is important to understand that the length of the suppressor is usually much longer than the length of the barrel / muzzle device / suppressor interface geometry. A small deviation at the mounting interface means a much larger deviation of the suppressor exit hole. The deviations from nominal can also be additive which compounds suppressor misalignment.
The Geissele SAG is manufactured from hardened steel that has been ground 0.002” under nominal bore diameter. The outside diameter of the SAG is finely finished and straight to 0.001” over its length. Geissele hardens the SAG so that it will not wear by sliding exposure to abrasive powder residue, pull burrs if it slides against misaligned baffles nor allow abrasive particle to embed into the surface of the gauge.
There can be a wide variation in barrel bore diameters and bore straightness. 0.002” under nominal bore diameter has been found to be the best size of the SAG that will fit most barrels. The long length of the SAG aligns the gauge to the bore; it is not necessary to have a very tight fitting gauge with the long length of the Geissele SAG
Note: The alignment rod may come branded by Geissele or by Surefire.
Available in 15" 5.56mm and 17" 7.62mm.