DIY Scout Scope

Last year I bought a JW-20 take-down .22 rifle, a clone of the Browning SA-22. This one was heavily discounted on account of not having a stock and was purchased along with a couple other guns in need of repair. I knocked up a stock for it and have taken it hunting for squirrels once or twice but have been unsatisfied with the iron sights. The rear sight is hard to adjust and I don’t like the geometry of the sight picture. Even with my roughed-out stock with adjustable cheek rest I found it difficult to achieve a consistent result with the setup whereas I had no problem with, for example, my Cooey 64 with its simple but effective open sights.

In evaluating options to improve the setup, I came up with a few possibilities. I could replace the iron sights with something better but would still be faced with the relatively short sight radius. Mounting the rear sight on the receiver was not an option because it is a take-down rifle and has a little bit of play where the barrel meets the receiver. This play also means that no matter how consistent a cheek weld I could create to the stock, I could not ensure a consistent head position with relation to the rear sight. Whatever sighting system I did use needed to be mounted to the barrel alone and would ideally be tolerant of sloppy head positioning. I could put a rail on the barrel and mount something like a reflex or red-dot sight. Or I could put on a scope, which was my preferred choice.

Donor Scope

Starting point: a cheap standard 3-9×40 scope

Spare parts

Various lens components — the detritus of a past life

The problem with mounting a scope is one of eye relief. Standard scopes would need to either be mounted to the receiver or cantilevered off of the barrel so as to come far enough back towards my eye when shooting. Mounting to the receiver was unacceptable for the same reason mounting a rear sight on the receiver was rejected. Creating a cantilever mount would have worked but would have added significantly to the length of the barrel assembly when the take-down rifle was apart. They joy of having a take-down rifle is that you can easily throw it into a pack or small case. I wanted to retain that benefit.

Ocular assembly

The ocular assembly of the scope disassembled. T,L-R: body, gasket, ocular lens. B,L-R: metal spacer, variable magnification lens, retention ring

The solution would be a “scout” or “long eye relief” scope, meant to be mounted well forward of the receiver. These are commercially available but even the inexpensive ones are pricier than their standard counterparts and they are relatively hard to acquire used. Fortunately, I used to do a lot of photograph and, because I had tinkered with adapted lenses at the time, I have a variety of spare parts on hand. I pulled out a box of old scopes I had and one of my boxes of old lens elements and went to work seeing what I could find. While scopes have several lens elements, I knew I would be concerned with replacing the ocular lens — the glass closest to the shooter’s eye. This lens focuses the light coming through the scope onto a point a few inches back from the scope where a shooter’s eye traditionally rests. I needed to find a lens that matched in size but would direct the light further back, allowing me to position the scope much further from my head.

Lens components

The replacement ocular lens came from a subassembly of a long-reel film camera lens. I have several of these intact as well as the parts from several more that have been disassembled.

As it happens, I had a cheap 3-9×40 scope where the entire ocular assembly could be removed just by screwing it out. The lens elements in the assembly could then be removed easily by screwing out a retention ring at the back of the assembly and dropping the various components out one by one — the large lens responsible for the variable magnification, a metal spacer that controlled its distance from the ocular lens, the ocular lens itself and then a small gasket meant to keep moisture out of the scope barrel. I also had on hand various lens elements from some long-reel cameras that were used to take school photographs back in the day when such things were done with film. One of the lens elements was a convex/concave lens that, when it replaced the convex/convex ocular lens of the scope, moved the focal point much further away from the lens while retaining the upright image.

After confirming that this setup would work, I put on some gloves and re-assembled the scope, cleaning each element as it went back in. I then bagged up the old lens in an envelope on which I have written the details of the hack in case I ever need to revert the scope to its original configuration. I had already affixed a weaver rail to the barrel so it was just a matter of mounting the scope with some rings I had on hand and bore sighting it. I will properly zero it when I am next at the range.

Norinco JW-20 with mounted "scout" scope

A Norinco JW-20 with roughed out stock, attached rail, and “scout” scope.

Leave a Reply

Your email address will not be published. Required fields are marked *