The AA sight wing spring, a shaped leaf spring, not to be confused with the coil spring for the rear site level adjustment latch, is shaped to fit into the slider sight wing slot alongwith the sight wing itself. It is just a matter of unscrewing the sight wing screw, removing the wing in its vertical position and using sturdy tweezers to remove the leaf spring, and reinstalling onto the other slider. The shape of the leaf spring may differ depending on arsenal, age or what ? but one example I had was an issue when I used a spring off of a Nagoya wing and attached onto a T-K long wing. The spring did not have the correct contour and the wings does not really "click" into each position, a bit on the loose side.
Could not resist taking a wing off since I had one of Rodents rifles here. I took some pictures but for some reason I can't post them. The tail of the spring is held in a small dove tail groove and there is a punch mark to stake the spring in. You have to be very careful in pushing the spring back out of the dovetail. The spring looks like the @ sign if you straighten the tail out. First take the wing screw out, take the broke piece of spring out and insert the replacement. You will have to use a small punch to get the spring to the proper place. Clamp the sight someway so that you can use a punch to put the stake back where the original stake was. Put the wing back on and you got it. Its not as easy as I just made it. If I had a replacement slider I would use it and let someone else way down the road worry about the inspection mark.
In my experience interchangability on rear sight parts can be sketchy. If you have a nagoya rifle use nagoya parts, mostly for originality but also because the japanese rifle parts are not as interchangable as US weapons. Sometimes still I have put a complete TK slider on a TK rifle only to have it not lock into the notch when all the way down, and on later rifles with the square cut base it can prevent the leaf from folding all the way down. My shooter type 99 is a kokura 21st that for one reason or another is missing the RH slider button, screw and spring. I found a complete kokura rear sight assembly to cannabalize and about 4 times a year for the last 6 years I have quested into the basement to try and get it together, I have yet to succeed. The wing springs are just a pain, and not worth the effort IMO. My only attempt to remove one broke the spring.
they are too much of a pain to change.Its easier to find a junker with a replacment slider thats completely correct arsenal and series.I usually dont replace AA wings unless Im SURE it had them originally,such as already having a broken set on the sight,as so many early transitional guns had the notch for them but never had the spring or wing installed(so also its likely unfinished internally)...generally T-99s seem to be closer to interchangable parts than the earlier guns,but unless you have a part from one pretty close from the same group it may not fit directly,as all guns were a "one off" especially later in the war. A good set of small files,a dremal tool,polishing cloths,brass driving tools, and some small hones and such are indispensable parts of a toolbench for working on arisaka ,as is at least one good magnifier (I have some small hand held,a couple clip mounted ones and two of the large lighted ones with the spring loaded swing arm on the bench).
I had a broken AA wing spring on a really nice early Nagoya. After reading about it here, figured it would be best and easiest to buy a new slider and replace the whole thing. So I got one from Numrich and it turned out to be a dog... the finish did not match (bluing not as deep, some minor surface rust) and it was actually bent up pretty good.
So I took a brass punch and knocked the broken remnants of the old spring out of the original slider, harvested just the spring from the Numrich donor, and installed it in the original slider. It went surprisingly well and looks much better.
The spring is flared at one end, like the leg on a pair of bell bottoms, so it only goes in and out one way easily. Once I positioned it by hand, I maintained some pressure on it downward to keep it from popping out, and just tapped it in gently with a brass punch and hammer (to avoid marring the finish). It's as good as new now. Attached is a pic to help visualize it.
I made a spring using a piece of thin saw blade. I used a propane torch to take the temper out. Filed the piece to shape and bent it to the correct shape. Then reheated it and dropped it in oil to retemper it. It then slipped into place following cartoonist's picture.
Yes it took a couple of tries, (and a couple of broken pieces) but it worked.