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Discussion Starter · #1 ·
I have a SAI NM. I originally had the FH without the bayonet lug. I liked the looked of the original USGI with the lug. I purchased a Fulton Armory part reamed to NM specifications.

Problem:
I had the FH on correctly without any problems. I went out to my families New Mexico ranch and did a lot of long distance shooting. It was great. When I got back I wanted to break the rifle down. I haven't done so in about a year (fully). When I re-installed the FH with castle nut and the hex screw I had problems. The screw did not go in fully. I do have the pliers and have the originals manual (USGI) & M14 book. Still issues.
Anyone have any tips and tricks? Pictures for installation? Run into this problem? I would appreciate any help y'all have to offer.

Thank you.
 

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Your problem has a pretty simple fix, your castle nut is not properly aligned. Simply adjust the castle nut a little and reinstall the set screw. The opening in the castle nut does not leave a lot of room for error in alignment.

You can use an allen wrench thru the set screw hole to get you close.
 

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Expanding on BLACKTAIL 8541's advice, set up the rifle so you can look through the sight where the castle nut goes with some white paper behind it for contrast. You should be able to see the set screw as it begins to enter that window when you tighten it. If it stops just as it touches the castle nut, you need to back off the set screw and tighten the castle nut just a bit, then try tightening the set screw again. Eventually, you'll see the set screw begin to disappear into a notch in the castle nut.
 

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M1A is right as usual, you need to be able to see in there, try taking the screw completely out and look in with light while tightening castle nut, its easy that way. What happened most likely, is carbon build up on the end of the barrel between the flash and the barrel end, check it if your old index for nut tightening is off now, also for trash down in the opposite seating surface of flash suppressor. If all else fails, you can emory cloth the back off the castle nut down some to get better index on next set of holes. It doesn't take hardly anything off to do this, so be careful !!
 

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All solid advice. Remember, when you "break your rifle down" removal of the flash hider is not a part of general maintenance, IMO. In fact, I NEVER remove it once set. If I get the rifle wet, I simply displace debris or water with WD40 and use a compressor to blow the WD from the nooks and crannies. That is not a spline that I want to wear by continual removal, besides....Ammo is too expensive to re zero every time.

Maybe it's just me, but once it's right I don't mess with it.
 

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Being right at the muzzle, those aren't splines you wanna do much peening on, either. The old Garand, you can peen the heck of it cuz the gas cyl locks on farther back where barrel is barrel, no flash suppressor to deal with. But muzzle and leade are two places where you wanna minimize disturbance unless it's just to freshen a crown.
 

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Discussion Starter · #7 ·
I took the rifle all the way down because I was doing a lot of shooting in the desert sand environment of New Mexico. It had a little sand on the outside, but nothing really major. I could have cleaned the rifle without taking it off, but since this SAI NM being my pride and joy - I really wanted to make sure I did a great job.

My next question is:
How tight should the FH and castle nut be? When I loosen the castle nut to allow the screw space to enter, the FH is somewhat loose. I am 99% sure this is a no-go. Any tricks to manipulate the castle nut when installing in order to get the correct fit?
 

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Yep, just file a very little bit off the back of the nut, and sand it smooth and retry next set of holes, take it easy though, it don't take much.

Tightness means about average pull with the gas cylinder wrench in one hand and the castle nut pliers in the other, pulling in toward each other, no need to get carried away though. Place the gas cylinder wrench handle at six o'clock as usual and the pliers at three or four o'clock and this will give you plenty leverage.
 

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Discussion Starter · #9 ·
Thank you for the tip. I did not think about that yet.

I do know my FH is aligned properly though. I don't have the official tool, or the BAD T1 (yet). One day I will. Right now tuition for graduate school comes first. I use a straight rod tool that is comparable from my Dads hobby shop.

I will work on my FH tomorrow morning and let you know about the results. Might try and take pictures of the M1a as well.
 

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...
My next question is:
How tight should the FH and castle nut be? When I loosen the castle nut to allow the screw space to enter, the FH is somewhat loose. I am 99% sure this is a no-go. Any tricks to manipulate the castle nut when installing in order to get the correct fit?
Not to overthink this but I wonder if it depends on how tight the FS is before you tighten the castle nut. With the splines evenly spaced around the interior of the back of the FS, if their fit in the barrel's grooves is tight to begin with, the FS will not only resist moving along the barrel but also up and down or side to side (the top spline might be able to rock in its groove, but then the other two splines would want to twist sideways, so the FS is effectively held in position). In that case, the castle nut's job is mainly to keep the FS from being blown off. If the FS has some wobble, then the castle nut has to pull the FS tightly enough to the muzzle to keep it from moving. I've always thought that over-tightening is bad but I think a wobbly FS is worse. And even if it feels tight in your hand, imagine what the muzzle blast can do.
 

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Ah just grab a framing hammer and rap it real good until something bends, it ought to seat very nicely SGRIN

Seriously, I usually clamp the whole receiver in to the soft jaws of my vice and then lightly tap the front of the FS with a plastic hammer while turning the castle nut; no I don't pound on it like you would a nail, I use judicious taps and as square to the face of the FS as I can. This usually gets a little more movement out of the castle nut and the screw goes in all the way. Then I turn the castle nut back against the screw.
 

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Discussion Starter · #12 ·
I was able to re-install without any sanding or grinding GI8 As someone mentioned on a post it was misaligned with the castle nut because I was tightening too much. Everything is great and thanks for everyone's input. Even a simple problem is a problem. It was fixed with the help of the great members of the forum.
Thanks.
 
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