Preppers Armory: Zeroing Red Dots

In previous posts I talked about the process of mounting and zeroing scopes. When used on rifles, red dots can be treated pretty much the same way as other optics. However, on handguns, especially compact pistols, there are some additional challenges when sighting red dot sights, also called RMRs for Rear Mounted Red Dots.

Sight Picture

On rifles, most red dot sights are set up to either bottom third or co-witness with the iron sights, if any. These two terms mean that the iron sights either appear below the dot, generally in the bottom third of the viewable area while the dot remains in the center, or the dot lines up precisely with the existing sights. Handgun RMRs frequently co-witness with the pistol's iron sights, which can make sighting in the red dot easier if the iron sights have been properly adjusted.

Co-Witness Options

Boresighting

If using a spud-type boresight, either collimator or laser style, the bore insert may be too long to seat properly in a handgun barrel, with the end of the spud impacting the breech face before it can solidly fit the muzzle. Magnetic or laser cartridge boresights should still work as designed.

Old school boresighting, where the target is viewed through the barrel and the sight is adjusted to coincide, obviously won't work with a semi-automatic pistol. Mirrored barrel inserts have been available now and again over the years for use with revolvers; good luck finding one, though.

That leaves the most fun option: actually shooting the gun and adjusting the point of aim and point of impact. When using this technique, the most important aspect is having the pistol properly braced. A Ransom Rest or something similar is ideal, but very pricey for both the base unit and the grip adaptors. I 3D printed a rest for sighting in my firearms.

3D Printed Rifle Rest

A traditional commercial rifle rest, sandbags, or even a bunch of tightly rolled or folded cloth can all work nearly as well as a fixed rest, as long as the shooter maintains consistency, grip, position, and orientation of the firearm.

Zeroing Procedure

1. With a handgun, the rest and firearm should be positioned so the shooter's forearms are also supported. With a long gun, this applies to the elbows.
2. Set up a target at a known range. I prefer starting handguns at five yards and rifles at ten, just in case the sighting system is way off. Having the dot contrast with the target is important for proper visibility. 
3. Once this is done, load five rounds into the magazine or cylinder, and make ready to shoot.

I prefer using five round groups. While three rounds are traditionally used for sighting, I've found that five reduces the uncertainty considerably. For example, if I have two shots close together and one flyer off to the side, I have to wonder if the ones in close proximity are coincidental or a clear representation of the firearm's potential accuracy, and I just pulled one shot. Meanwhile, with five round groups, this issue practically vanishes, as four shots close together with one flyer is much easier to judge.

Adjustment

As with other optics, most RMRs will have some system for adjusting the emitter. A fairly common one is recessed screws turned by a small hex wrench, which is frequently supplied with the optic.

Pay close attention to those adjustment points; they should be marked with an arrow and the letter U for up or L for left. Rarely will you see D for down or R for right marked on them. If there are no markings, check the manual or manufacturer's website.

Consistency is key, so fire five rounds while maintaining the same sight picture. Hopefully they are all in close proximity, even if they aren't at the point of aim. Tune the vertical and horizontal adjustments, and repeat.

Within a few cycles of this process, the shots should be landing where the dot appears on the target. If necessary, put up a new target at the intended zero distance, and repeat for final adjustments. At this point, the red dot should be properly sighted in, and barring a problem shouldn't require any further adjustments. 

Final Thoughts

The only other thing we'll need to do is make sure the battery is changed regularly. Some of the newer red dots have auto off and shake-awake features, with battery life measured in tens of thousands of hours. There are even units with small solar panels to keep the battery topped off when exposed to light.

Whether the optic has these features or not, find out how long the battery actually lasts, and make sure to schedule replacement within this window.

Shoot often, shoot safely, shoot accurately.