Understanding and Adapting to AR Offset

Back in the old days we never considered offset for the M-16. When it was better understood firearms trainers would stand on the line yelling “remember your offset”. What we have found from after action reviews is that under the extreme stress of life...


Twenty years ago the street cop needed to understand the workings of only two firearms; his duty pistol and the pump-action shotgun in his cruiser. When I started my career as a policeman my Chief carried a 4-inch S&W L-frame on his belt and a J-frame on his ankle. Our duty shotguns were Remington 870’s with wooden furniture and leather shell holders on the stocks. The term patrol rifle, if it had been coined at all, was rarely uttered.

Fast forward to the year 2011 and you are just as likely to encounter a Stoner-based AR rifle of some sort as you are shotgun. Patrol rifle and black rifle have become nearly interchangeable terms.  

One of the greatest attributes of training new officers on the AR rifle is the fact that it operates in a semi-automatic mode, just like their duty pistols versus the manual pump action of the shotgun. The down side is the more complex set of controls on the AR; safety lever, charging handle, bolt catch, etc.

What is Offset?

The term offset refers to the difference between the centerline of the gun’s bore and the aiming point of the gun’s sight system. This sight system could be as simple as a brass bead or as complex as an ACOG magnified optic.

When we are discussing duty pistols or traditional shotguns the distance between the top edge of the front sight and the center of the bore will be less than an inch. For instance, the bore to sight offset on my GLOCK17 with XS Big Dot is 0.54 inches. Using factory sights it’s less than a half inch.

Now consider the standard height “A2” front sight housing on an AR rifle. The offset is just a bit more than 2.5 inches. Add a magnified optic of some sort and like the Trijicon ACOG or the new Leupold HAMR and the offset expands to 3.5 to 4 inches. Many magnified optic makers will install a mini red-dot sight atop the magnified optic for fast, close in shooting. The offset now climbs to a startling five inches.

Big deal you say? Consider this, when police officers use a patrol carbine they are generally using it as a power tool as opposed to a long range, precision instrument.   Patrol rifles aren’t sniper rifles and we don’t expect patrolmen to take out enemy personnel at five hundred yards.

A patrol rifle will be most often used within twenty-five yards. Inside a building that distance shrinks considerably. AR offset is most pronounced from the muzzle out to around seven yards. What looks like a solid shot ends up impacting three inches low.

In the police arena we have to account for every shot fired and the real world is filled with people that should not be shot. Compound this with the fact that most bad guys don’t give the full-frontal B-27 silhouette that we all practice on. Instead you get a partially obstructed, moving target that likes to duck behind cover.  

Offset Solutions

Now that we’ve accepted the offset issue, let’s consider some solutions. The simplest and easiest to use is the CSAT Rear Sight Aperture from XS Sights.   The CSAT rear sight aperture replaces the standard aperture found on most A2 rear sight housings.   Designed by Paul Howe, retired MSGT US Army, Special Operations, the CSAT rear sight compensates for bore offset and allows the officer to use their AR sights like standard pistol sights.   No mental gymnastics or calculating under stress.

The next solution to offset for a rifle with magnified optics is to mount a set of canted sights at 45 degrees left or right of the optic. Dueck Defense offers a set of iron offset sights with AR front and rear hardware.   To mount this sight option you’ll need a Picatinny top rail on the front and rear of your rifle.  

LMT and Predator Tactical offer platforms that allow you to mount a mini red-dot of some sort at 45 degrees. This takes the mini red-dot from a 5 inch offset down to a more manageable 1 to 2 inches. Naturally, the mini red-dots are windage and elevation adjustable allowing you to BZO your close in optic for practical distances of 10, 15, 20 yards, etc.    

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