Wrench size for sight screw


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Old 01-20-21, 09:14 AM
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Wrench size for sight screw

The front sight on my bull barrel Ruger Mark IV 22/45 came loose. I thought I had the right wrench to tighten it but ended up stripping it. I could get it out and have a replacement on order but, before I strip that one as well, does anyone know what size hex key actually fits this screw? I'm normally pretty good at searching the internet but coming up dry on this one.
 
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Old 01-20-21, 09:37 AM
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I just try until I find the size that fits. It is quite possible that it is metric. They are small screws so even with the right size Allen wrench it is still possible to strip out if you tighten too hard. And, make sure your Allen wrench is nice and sharp. If the end is worn with the points of the hex rounded even slightly, take it to the grinder and remove the worn part so you have 100% good wrench to work with.
 
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Old 01-20-21, 01:54 PM
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If you have vernier calipers, measure across opposite flats. If you have number drills (#1 drill =.228 inch), find one that just goes into the female socket. Both of these approaches should give you the dimension to get the correct size wrench. If you have neither, buy a machinist scale with a 64th scale and use a magnifying glass to get measurement across flats. You should be able to read the dimension within +/- .007 inch, close enough to get you to the correct SAE or metric hex wrench. Do you know if you can get a replacement screw with a nylon insert in the threads?
 
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Old 01-20-21, 02:11 PM
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To clarify - we're talking something in the neighborhood of 5/64"; I think this thing is smaller than you might be envisioning, Bob. Also, to my knowledge, no screw with an insert is available.
 
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Old 01-20-21, 02:33 PM
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So I found someone online who says it's .05". Didn't even know that's a size but they do apparently make hex keys that small.
 
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Old 01-21-21, 07:11 AM
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