I was putting together a .308 dpms lower for a rifle I'm building and ran into a problem. The screw for the bolt catch mechanism which appeared to be a 1/16" allen head seemed to strip out (not the threads the head). I turned it all the way in and was NOT putting a lot of pressure on it and it just kept turning. So, its in, but it feels kinda wierd not knowing whats up. I tried standard and metric sizes before putting it together in the first place and it seemd 1/16" was the correct size....
It should have been a allen. That is spec. I would never leave a stripped out head screw in a gun. Take care of it now. You also do not know how tight it really is. You can hammer force in a Torx bit to get it out if you do not want to drill and use a extractor bit. Order a new one or after you get it out go down to the local ACE or other hardware store and see if you can find a match on threading.
It is an Allen head. I do not recall what size because I always just grab the wrench that fits. It does screw in quite a ways before bottoming out so are you sure you're just not freaking a little and it is not all the way in? A 1/16 wrench sounds right but you have to put a lot of force on it to strip it out. The three of mine that I have done I just turn it in until snugs up and use just a tiny amount of 242 blue Lock-Tite on the threads, NEVER the smooth part (shaft). I've never had a problem with it walking out on my .500 Phantom. The other two have not been shot yet.
You are not going to find it at a hardware store so don't bother looking. Order it from Midway, they have it, $4: link. As you know, the front part of the "screw" is not threaded for the bolt catch to pivot on and only the rear section of the screw is threaded. And since the unthreaded part of the screw is a smaller diameter than the threaded side, the "left" hole in the bolt catch pin housing is not threaded and smaller than the right side threaded part. If you try to use a screw that is threaded all the way it will not go in the left side of the bolt catch pin housing.
It appeared to be an allen head. I tried standard and metric. The 1/16" was the only thing in the ballpark, and it was a "tad" "teeny" bit loose!? After a day or so to reflect I would feel better with it outta there. The torx idea sounds interresting...
There is also a bit of tolerence on the drivers. You might try a brand name wrench if you haven't already. I buy these by the box at times to include with other hardware. If the end of the wrench is beat up or rounded a bit, this will make a big difference on a wrench that small. Sometimes the screws vary as well. If you can't get a spare easily, p.m. me. I have a couple of new DPMS kits that I could steal a part from.
all the best,
Thanks for all the replies, and especially to eaglemike for the offer of a screw. I had contacted DPMS also and they are going to send me a new screw. Really great of them. They were nice about my request. I do want to replace it. the torx idea sounded like a good approach.