Rimfire Rifle Aperture Sights

I have found that I can shoot more accurately with an aperture sight than with a notchtype sight. The small diameter hole in the aperture allows me to better center the front sight versus the typical larger rear notch. Increasing the sight radius is a proven means of improving accuracy as well. I bought an aperture sight for my Ruger 10/22 that replaced the original front and rear sights and increased the sight radius from 18 to 24 inches on a 20-inch barrel, a significant 33%.

The rear sight is installed using the two rearward scope base mounting holes and the new front sight assembly is installed in the existing dovetail. The sights are from Tech-Sights, LLC (Tech-Sights.com, and they offer two types for the 10/22: the TSR100 "GI" type with two apertures that can be flipped forward or rearward to adjust for distance and the TRS200 with an elevation adjustable rear aperture. Both have windage adjustment on the rear sight and an AR-15 type elevation adjustable front post.

I bought the TRS100. The company also several other sights for a variety of rifles. I performed a baseline test with the original sights, firing three groups of five shots at 25 and 50 yards. The sights on the 10/22 had fiber optic inserts which I thought might be better than the older style notch sight from a previous model. Turns out that the rear sight fiber optic did not really help, at least in bright daylight. I then installed and zeroed the new sights and repeated the tests.

The instructions are easy to follow, and I had no problems installing the sights. The original front sight is drifted out of the dovetail and the new sight tower is installed and locked into place with three screws. The rear sight is installed on the receiver with two screws. The aperture sight and its longer sight radius Below center: 10/22 original rear sight. reduced the average group size by 50% at 25 yards and 46% at 50 yards.

I took my time when doing the accuracy tests, trying to be as precise as possible so as not to shade the results. The results are in the accuracy table. I used CCI Standard Velocity ammo for all the tests. The GI-style sight looks good on the 10/22, giving it a M1 carbine appearance, although the TSR100 front sight is considerably taller. I have a couple of issues with the adjustments, however. The windage adjustment is hard to turn due to the stiff detent and no grip surface.

I used a 3/32" diameter punch to depress the detent and turn the wheel. The front post appears to be the same as on an AR-15 sight but has five slots for the detent whereas my AR-15 front sight tool only has four pins, so it didn’t work on this sight. I had to push the detent down with a 1/16" diameter punch and turn the post slightly to keep the detent depressed and then push

on one of the notches to index the post to the next notch. Fortunately, it didn’t require much adjustment to zero the sights. With the stiff detents, the sights won’t get knocked out of alignment due to rough handling. I was impressed with the quality of the sights and consider them a worthwhile improvement at a reasonable cost despite the rather awkward adjustments. I have a Savage B22 bolt action in 22 Long Rifle that has proven to be very accurate. It has a free floated 21" barrel and the Accu Trigger.

I wanted to add an aperture sight with a longer sight radius but, unfortunately, Tech-Sights does not offer one for that rifle. I decided to build an aperture rear sight that would work with the original front sight. The front sight is attached to the barrel with two screws as opposed to a dovetail. I determined the height of the aperture by using a straight edge from the top of the front sight blade through the rear sight notch and measuring the height at the rear of the receiver.

This showed me that the rear sight had to have a low profile to avoid needing anew, taller front sight. The rifle had two scope bases installed at the factory, so I removed the rear one and used the holes to mount the aperture sight base. I designed the aperture sight with elevation and windage adjustments. I milled and filed the bottom of the sight base to match the profile of the receiver.

The elevation adjustment is provided by the bar mounted to the base and the windage adjustment is on the aperture bar at the rear of the elevation bar. Each is moved by a small screw. The elevation bar pivots on a small diameter pin with elevation adjusted by 6-48 screw that goes through the bar into a tapped hole in the base. A small spring is located under the bar to provide upward pressure and ensure the bar moves upward when a higher point of impact is required. The windage screw is a 1" long 6-32 screw.

I would have preferred to use a 6-48 screw but could not find one longer than 0.5" at my local supplier. I drilled a pilot hole for this screw through the elevation bar and the aperture bar at the same time to ensure proper alignment. I drilled and tapped the aperture bar for the 6-32 threads and used a #29 drill to provide minimal clearance holes in the elevation bar. A small diameter spring was shortened to a suitable length and added on the left side of the windage screw to eliminate endplay.

I used a nyloninsert lock nut on the end of the

Base, elevation bar, aperture bar, adjustment screws and springs. screw. The nut is large enough to easily adjust the windage but is not obtrusive. This turned out to be a simple and effective way of assembling the parts. Granted, it is not as an elegant design as the Tech-Sight but it works fine. The elevation and windage screws work smoothly with the needed precision and stay zeroed. The aperture has the 0.062" diameter hole that I prefer. I ran the same tests as on the 10/22.

The aperture sight increased the sight radius from 16.75" to 24.5" (45%) and together, they reduced the average group sizes by 52% and 47% respectively as shown in the table. So, how much of the improvement is due to the aperture sight and how much is due to the longer sight radius? The accuracy on the 10/22 was improved by an average of 48%. The sight radius was increased by 33%, so was the additional 15% due to the aperture sight?

The Savage sight radius increased by 45% but the accuracy improvement averaged 49.5%. There is probably a limit to how much a longer sight radius improves the accuracy due to the law of diminishing returns. As I said earlier, an aperture sight typically allows me to center the front sight better but the notch sight on the Savage gave me a clear sight picture, better than on the 10/22. In my opinion, the improvement on the Savage was mainly due to the sight radius increase.

Installing the original sights at the longer sight radius or installing the aperture sights at the original sight radius would help answer the question but I am not inclined to spend the time nor effort to find out. The aperture sights and longer sight radius significantly reduced the group sizes at a reasonable cost. The cost for the Savage aperture sight was mostly my time and a few dollars in hardware as the rough material was left over from previous projects.

Someone with better eyes could likely shoot smaller groups than I did. This project had the right amount of technical challenge, didn’t cost much, and helped the winter months go by more quickly. AG