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Wednesday, November 10, 2010

Marbles Tang Sight- A Picture Disassembly Guide (see steps 1-4 to tighten) by Shasta

The Marbles tang sight is my favorite as I really like the click-detent adjustments for windage and elevation. Frequently the sight they recommend for a given rifle does not offer enough elevation to suit me.

I have solved this problem in several ways. One was to simply buy a taller-stemmed sight designed for a different rifle. At about $100 per sight this is not a cheap solution. For a mere $6 (from Buffalo Arms) I bought just the elevation stem, and swapped out the one in my sight for a taller one.

This job is not complicated, but working with very tiny parts that don't always co-operate can lead to some frustration and "blue" language. Be advised and proceed at your own risk!

Start by having the right tools on hand. A clean cloth on the workbench will help prevent lost parts. A magnet is also handy for keeping track of small parts.
The first task is to remove the windage knob. Some are held on by a set screw, but most I've seen are held by a roll pin. I use a very small nail with the point ground flat to punch out the pin:

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Be very careful here because when the windage knob is free to slide off the windage screw, there are two very tiny ball bearings that will fall out. Keep the job close to the bench and don't let those little buggers get away!

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Next remove the windage screw. It has two holes in the head, and a cut-off paper clip makes a good tool for spanning the holes and turning out the screw.

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With the windage screw removed the elevation assembly is free. In the sight base under the elevation assembly is a square-shaped piece of spring steel with a peak fold. This is the detent spring that holds the elevation stem upright. If the sight has a loose or floppy elevation stem, this spring can be tweaked or have a shim placed under it to tighten things up.

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Now comes the tricky part; using an appropriate size Allen wrench remove the screw at the base of the elevation assembly. Again keep the work close to the bench as there are more of those little tiny ball bearings about to come falling out.

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By carefully turning the elevation base while holding the knob with the Allen screw hole facing the bench, eight ball bearings will come out one at a time. There is also a single ball bearing used as a detent between the elevation knob and stem base. You can see it in the picture still in place. It will fall out as the knob and base are separated, so be very careful. The dime in the picture gives some idea of how small these parts are.

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This is what the elevation knob and base look like when separated. Note the pin passing through the bottom of the sight stem. It rides in the slot cut in the elevation base and this is what keeps the eyepiece always facing the correct way.

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Using a needle-nose pliar remove the pin. The eyepiece stem can now be un-threaded from the elevation knob.

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Here are the eyepiece stems I had on hand. You can see there is quite a difference in length. The shortest one is from the sight pictured. The center one is the replacement.

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Here I have the new stem threaded throught the elevation knob and the alignment pin back in place.

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As they say in all the manuals "Reassemble in reverse order".

I find it helpful to use a speck of grease to hold the detent ball bearing in place when putting the elevation knob-stem assembly back onto the elevation base. With the detent in place, hold pressure to keep the components tightly together while feeding the eight ball bearings back in one at a time through the Allen screw hole. They fit in a groove on the elevation base and may require a bit of assistance from a piece of wire or a nail to work their way all the way around. Don't force them! They will all fit with a bit of manipulation. Once all the bearings are back in, reinstall the Allen screw.

Now we are back to the basic components ready for final assembly.

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This is a good time to be sure the square spring for the elevation stem assembly is working properly. Place the spring back in its recess in the sight base. Holding the elevation assembly in place, thread the windage screw back in all the way. Now flop the sight stem up and down a few times. It should have good resistance and be free of play in the upright position. If not, remove the windage screw and tweak or shim under the square spring as needed. Once everything is working, hold the sight on its side with the detent surface facing the bench. Carefully place the two windage detent ball bearings onto the windage knob and slip it back in place. Replace the roll pin (or set screw) in the knob and the sight is ready to install on the rifle. Simple, EH?

This is the sight back on the rifle. Because the stem is long for the elevation knob, some of the threads show even with the sight all the way down, but now I have plenty of elevation to play with.

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Good luck!! SHASTA

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