Installing Peeps on the Barra 1866

I’m not the greatest shot with open sights, but I was pretty certain I could get better than 1.2″ groups at 25 yards with the Barra Cowboy Series 1866 with a better set of open sights. It is nothing for me to spend a good chunk of cash mounting a scope on an air rifle, but the 1866 lacks a scope mount. Instead, I decided to order a Williams 5D receiver sight designed for the Winchester 94/36 rifles.

The Barra 1866 with a custom set of sights.

There were several challenges that had to be overcome to make this work. The sight was designed for rifles with a thinner receiver than the 1866. To overcome this, I carefully sanded material from the mounting plate:

Note the unfinished surface. This is necessary to give extra sight adjustment to the right.

Now that the mount was sanded down, I could get a little more adjustment to the right. The peep section was reinstalled in the lowest setting. I then added a small amount of super glue to the mount and carefully positioned it on the side of the receiver with the peep section resting on the top of the receiver. Once the glue cured, the peep section was removed in preparation for screw holes to be drilled and tapped into the receiver. The left hand receiver is also removed at this time:

The sight base ready for the next step.

I took a #31 drill bit and carefully drilled holes through the holes in the sight base. It is important to drill these as square as possible. The holes were then threaded with a 6-48 tap. A tiny drop of superglue was added to the threads of the screws before securing the sight base to the receiver:

The sight base and left hand receiver in place.

With the 1866 put back together and the peep installed into the base, the stock rear sight was removed from the barrel shroud. Testing the peep sight with the stock front sight showed improvement, shrinking my groups at 25 yards down to .98″ CTC. I did run into a new problem at this point – the front sight is too low for this peep sight, causing my groups to be high.

I designed and 3D printed a new front sight that doubles as a LDC that backdrafts into the shroud. To keep this backdraft contained in the shroud, I also designed and 3D printed a barrel stabilizer. A collar was also printed and installed inside the shroud to cover the holes from removing the front sight and faux magazine. I used a glazing putty to make those holes flush with the rest of the shroud and hit it with a quick spray of gloss black spray paint to blend everything in.

The result of all this work? The LDC isn’t mouse fart quiet since it is only 45 mm long. It does take the pop out of the shot at full power and makes the gun very backyard friendly. The barrel stabilizer combined with the LDC and upgraded sights certainly paid off, check out this group at 25 yards:

.640-.177= .463″ CTC! A huge improvement over the stock sights at 25 yards!

There’s a fair amount of work that goes into this modification, but it is worth every bit of it. Being able to shoot groups like that at 25 yards makes the Barra 1866 a solid hunting platform and a real performer in the backyard range. If you’d like to do this modification to your 1866 and need some help, feel free to send me a message.

Author: Geo

I've enjoyed shooting and hunting with airguns since my early teen years. For well over a decade, I have shared my passion for airguns on this website.

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