I've got an M14 with NM-style 1/2 MOA windage adjustments. Had it installed by a gunsmith here in AZ about 5 years ago.
Knobs got all gritty and I started getting weird behavior from the rear sight... the rear sight would fall under recoil and lower.
I disassembled, tightened the elevation knob onto the shaft as described by Walt Kuleck in his M14 maintenance book, cleaned, lubed, reassembled.
Except, I didn't know that the 1/2 MOA variant of turrets used a detent ball similar to the AR-15 rear sight windage detent.
So, it escaped me somewhere and is happily hiding on the floor or been vacuumed or swept up.
Can anyone tell me where I can find a new detent ball? Did this setup also have a spring in there too, or did it rely upon the latent spring pressure of the rear sight assembly when assembled?
The ball in the M14 system appears to be the same size as the one in the AR-15 system. Definitely smaller than 0.177, since I tried a BB and that was too big.
I've checked Brownells and Midway. They'll sell me a whole rear sight assembly, but they don't have just the ball detent.
It is a standard ball bearing and there is no extra spring, just a ball between the knob and the sight frame. If you call Springfield they can give you the size or ship one out to you.
Found out it's a 1/8 inch steel ball bearing.
Nuttin' special.
I can get a bag of 100 of 'em for $5.