M1A: Loctite the Peep Elevation Screw?

[BerettaNut92]

So I'm sighting in my M1A. My shot groups became vertical lines and I realize that the rear sight is slipping down so after I while I figure to tighten the screw that's on the elevation knob.

I tightened it so long ago (months and months and months ago) that I forgot about it, but I guess it worked itself loose after a while? Should I loctite it in or is there something else I'm missing (like some kind of retention screw like the castlenut has up front that I totally missed?)

PS when I got my new muzzlebrake in, SA sent me another NM frontsight and it sights in 20 or 21 clicks up.

 

[ms1200]

i wouldn't use loctite. on my m1a i have made it a habit of making
sure the screws are tight each time i clean after a trip to the range.

 

[mcole]

yopu might try just a touch or so of clear nail polish. works well on my buckmark, where the rear sight screw has a tendency to loosen up. and the good news is that it will allow the screw to be removed or turned very easily and quickly. mcole

 

[Dave Markowitz]

One thing you might try, although it'd be more expensive, is to replace the rear sight with a WW2-style M1 Garand "lockbar" rear sight. On these, you turn a locking bar to loosen the rear site so you can adjust it, then re-engage the bar to lock it in place. IME, it's much easier to use than the postwar-style sight found on most M1s and M1As.

 

[hps1]

"so after I while I figure to tighten the screw that's on the elevation knob"

Your'e tightening the wrong screw. The screw on the elevation knob on both the Garand and M1A (basically same sight) is so that once you are sighted in, you can loosen this screw and index the sight so that you can set known distance range settings by lining up the proper yardage on the elevation knob.

There is a wave spring washer inside the elevation knob which holds the elevation detent tension so rear sight cannot slip down.
Proper adjustment on rear sight tension is set as follows:

1) Run rear sight all the way up.
2) Try to push down with your thumb on top of rear apperature.
3) If you can push down, increase tension on the wave spring by tightening the spanner nut in the windage knob. This nut can be tightened with a special screw driver ground with a slot in center to clear the end of elevation spindle. Note: There is a special lock built into this adjusting nut that requires it to be tightened in 1/2 turn increments. You will feel it drop into the "groove" when you reach the proper spot.
Tighten 1/2 turn and try it until you can no longer push down the rear sight with your thumb.

A word of caution, do not tighten more than necessary as it makes your windage knob harder to turn, the more pressure you put on the nut.

If, you have difficulty adjusting windage when elevation tension is properly set (this sometimes happens), you can make windage changes easier by pushing in on the screw in center of elevation knob with one thumb while turning the windage knob w/other hand.

"SA sent me another NM frontsight and it sights in 20 or 21 clicks up."

This is not good. It makes your rear sight much too high for proper cheek pressure at long range (600 yds). To help this, you can carefully file the top of the new front sight off so that your 200 yard zero is somewhere between 5-8 clicks up from the bottom. If you ever shoot your rifle at 100 yards, DO NOT go below 5 clicks @ 200 (if 200 is where your are sighting in) or you will be unable to get low enough for 100 yds. There is usually 3 clicks difference in the M1/M1A between 100 and 200 yards.

Rough rule of thumb, IIRC is that .003" = 1/4 minute but don't trust my memory all that much, take your file to the range and cut 'n shoot.

Do not use locktite on your sight.

Regards,
hps