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View Full Version : Thompson Center Contender IHMSA / Lyman rear sight



ohland
06-22-2011, 12:12 PM
Picked up an IHMSA / Lyman rear sight for a Contender.

http://castboolits.gunloads.com/imagehosting/179094e020c3b36f46.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=1267)

It left me sorta dejected, after running the elevation and windage screws, it seemed a bit imprecise. The black finish is not hard, and IMHO, will start to wear off rather quickly. After disassembling the sight, I put 'er in a ziplock, tossed it into a cabinet, and wrote it off as experience...

But.. while scouring the net for 25-35 or 256 Mag info, I ran into an article of a Mike Bellm Contender... Oddly, the sight is mentioned as "old Side Saddle Williams Silhouette rear sights"

http://seanhhi7364.tripod.com/producttests/id7.html

http://castboolits.gunloads.com/imagehosting/thum_179094e02136ce19e4.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=1268)

There in all it's glory is a Lyman base, with a Williams FoolProof stem... This intrigued me greatly. Grabbed my FP-Deluxe stem and diddled a bit. First, the Lyman sight dovetail is a bit shallower than the FP dovetail. You can take care of this with a good file (the Lyman base is steel! Thought it was aluminum...). The next doesn't fit is the elevation screw. The Lyman screw is bigger and the Williams screw sorta half-buttocks screws in, but not loose enough to slide into the hole.

I see two reasonable mods, the first being drilling at right angles to the thread and pin in a short length of round stock. Then drill out the existing threads a bit, drill entirely through the round stock, then drill and tap. The sight should be cross-drilled for the plug, then pulled out, use a small bit to align the existing screw thread to the drill / mill, place in vice / fixture, pop in plug, pin it, now drill for the Williams elevation screw. Or just cross-drill n tap for a short length of a machine screw, cut a slot in the stub, add some LocTite, then stick er in. That screw will not turn while being drilled...

The second approach is to turn a very thin collar around the screw, then insert into the drilled out original thread. This looks dicey, as there isn't a lot of thickness to drill out the existing thread.

Now that I have taken a stab at it, the question remains- how much to machine out the bottom of the Lyman dovetail? The elevation screw needs to be aligned between the Williams stem and the Lyman base..

If idle hands are the devil's playground, then I MUST be an amusement park...

[smilie=6:

ohland
06-28-2011, 09:04 PM
Measured the Lyman and Williams elevation screw diameters and used a thread gauge to get the tpi.

Lyman dia: .135"
Williams dia: .135"

So both are a #6 machine screw.

Lyman is a 6-48
Williams is a 6-40

Result - the FoolProof elevation screw turns about three times, then locks up. I found something interesting today, stainless steel hypodermic tubing.

The max outside diameter of a #6 screw is .138", minimum diameter of the root is @ .110". The Lyman base is @ .200" thick around the elevation screw. Looks like an OD of .145 - .156 with an ID of .110 is workable.

Chuck up a 6-48 tap in a collet chuck to align the base, drill for the tubing, apply some Loctite permanent formula to the tubing, slip it in, let it set a bit, then tap 6-40 using a thread forming tap.

Anyways, thats my view of reality.

:veryconfu

EDG
07-03-2011, 01:25 PM
Just buy the 100% Williams sight.

ohland
07-09-2011, 10:29 PM
Just buy the 100% Williams sight.


Eh, why cast bullets when you can buy jacketed bullets? Why not go full auto vs single shot...

Its the technical challenge. Besides, the TC base looks like it belongs on the Contender.

All the parts should be home waiting for me when I get back on Sunday. And a bullet mold. And some other things that I forgot...:popcorn:

EDG
07-10-2011, 03:14 AM
Why not ride a horse to the range?

ohland
07-12-2011, 04:49 PM
Why not ride a horse to the range?

Don't have enough land to keep a horse. The "pasture" would be a trampled mudpit.

Thought of doing a press fit for the threaded tubing...

:popcorn: