Screw Thread Size?

I have a Model 99 in 300 Savage with a lever boss date code of 1957. When I disassembled it for a thorough cleaning I discovered that the 'breech bolt stop' was missing. The screw that held it in fell out of the receiver, it was floating around loose in there, but the stop itself was nowhere to be found. The threads on the screw look a bit chewed up, and the first couple threads in the hole don't look too good either, but deeper down look like they've never been touched.

So my question is this. Can anyone tell me what the proper screw thread is for this? As best I can determine, it appears to be a 5-40 thread. The threads on a 6-40 screw look to line up with what is left of my screw but the 6-40 is definitely a bigger diameter, and a #4 diameter screw appears to be smaller diameter. That leaves a #5, which I had never heard of before.

My hope is to find a bottoming tap to touch up the existing hole in the receiver and locate a longer screw to reach past the top couple threads that are pretty suspect.

Thanks for any help you can offer.

W

Measure the outside diameter of the screw. It may not be a UNF standard. Try ME (Model Engineers) threads. There are several from 1/8 to 1/4 that have 40 tpi. Brownells is one source of the odd screw sizes and taps often used in firearms. Sorry I couldn't be more help.

MacDR,

Thanks for the reply. I've never heard of ME threads before, and researched them a little last night. The screw measures 1/8th inch on the OD, which lines up perfect for a #5 size screw. I'll browse Brownells web page to see what I can find there.

Thanks for the help.

W