Friday, February 25, 2011

Modifying a T/C Rear Sight for a 22XX--Part 1

So, I think I want to use iron sights on the 2240 AirSource gun. Specifically, I'd like to use my Crosman LPA MIM sight--except it's currently on top of the 17XX match-style pistol right now. The LPA sight isn't ideal on the match-type gun (it's too narrow) so maybe I can come up with a more appropriate target sight and just swap some stuff around.

I bought this Thompson/Center rear sight unit on a whim at the Gun Shoppe about a year ago and threw it in the parts box.

I thought the curved base looked about right for a 22XX gas tube. And it is.

The only problem with the T/C sight is the leaf is much too narrow to acquire the correct sight picture on a 10-meter pistol target. The piece on the bottom is a spare leaf from an IZH-46M.

My initial thought was to simply attach the IZH leaf directly to the T/C unit.

Except the T/C is too narrow.

I could move the bolt holes, but where's the fun in that?

Removed the windage screw...

and the sight blade and spring came out.

Still too narrow. I like the idea of being able to interchange leafs of differing widths--and I'd prefer to have some uniformity, if there is such a thing. So it might prove useful to make the T/C sight accept IZH leafs. An adapter of some sort is required.

Went through the box of metal and found a piece of what's probably cold rolled steel. A small machinist square (they let anybody buy these things) confirmed that the sides were 90 degree angles. This is good--it means less work for me.

A bit of layout fluid and some quick measuring was next.

Almost all the numbers are arbitrary. I elected to make the "adapter" wider than the stock T/C blade then drill and tap mounting holes so the IZH leaf will attach.

Cut out a rectangle from the raw material then milled to length. (front to back measurement)

And squared up the width. I used 32mm as the arbitrary number. The piece just needs to be wide enough for the bolt hole spacing in the IZH leaf.

Milled out the clearance on the sides.

A "T" shape.

Reduced the height of the center boss on the top. It would work fine as it is, but it better fits the lines of the sight base...





Not shown: Milled, then sanded, the rear of the adapter at an angle. Want the leaf angled backward slightly to reduce glare.

Getting there. More to come in a couple days.

Monday, February 21, 2011

A.B.T. Shooting Gallery Rifle Disassembly, Part 4

Almost done…


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Oh, the second socket head setscrew.


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Removed.


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It retains the hammer/trigger assembly.


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The trigger is riveted, so I won’t remove it. The pin could be pressed out to remove the hammer and spring but I’ll leave it for now.


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You can see the spring and hammer.


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Pushing it in.


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That leaves the valve.


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A screwdriver should work as the valve stem can be pushed past the screw slot.


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Removed. No seal on it, although most of the air should just go out through the barrel. Maybe I’ll use some teflot tape although it’s a pretty tight thread.


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The valve stem wouldn’t come out. So I pressed against it through the air supply hole with a bamboo chopstick.


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Valve stem and seal. It’s fairly soft rubber and appears to be in good shape.


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Another view.


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This is what it would look like assembled. I notice there’s no spring to keep the valve seated on the seal, which is curious. I wonder if there’s supposed to be one?


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My bench after the disassembly. I’ll clean it all up and reassemble. I'll spend some time trying to understand better how the mechanism works. Then it’s a question of finding the proper ammo, making a cardboard tube for the ammo, and hooking up an air line.


If you have any useful information, especially a manual for the rifle, original cardboard tubes and ammo, etc. I'd love to hear from you. UPDATE: See here for a source for original ammo.


Sunday, February 20, 2011

A.B.T. Shooting Gallery Rifle Disassembly, Part 3

On I go…

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A small setscrew, there are only two socket head fasteners on the rifle.

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Removed and the barrel slides out of the block. The magazine tube is pressed or soldered in as far as I can tell.

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The shuttle.

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Slides right out.

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The lower bar keeps the bbs from falling into the valve, the upper has something to do with the cardboard tube of bb-s that is fed into the gun. Haven’t figured that out yet.

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A screw retains the feed ramp.

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Removed.

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A screw retains that spring.

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Removed.

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The leaf spring that allows the feed ramp to spring up.

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Removed.

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Two springs on the trigger mechanism.

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One removed.

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I left the other one in place, for now at least.

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Large head screw.

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Removed and the feed cam comes off.

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I don’t know what to call these parts yet, and I’m leaving them in place.

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The hammer & valve assembly is exposed.

More to come…