Quoted:
yea I tried to screw the bolt on without the grip....it got maybe 2 turns and went tight on me....cant get anymore......what is the size screws they use I think its an AR AR grip....standard carbine grip.....sorry new to ARs again....I am regularly an AK guy lol and dont think I would have to deal with this type of ship.....annoying
Without the grip on you should be able to see if there are any shiney spots or any metal shavings. Could have thread locker in there, which when its dry, the screw has to push that material out of the way. May feel stripped, the screw supplied with most MIAD already have blue thread locker on there. This is what you could be feeling. Chase the thread with a tap. Worse case senario drill and retap.
Post pics, hard to tell without them.