M14 flash hider wobble: Is my solution okay?

[AZRedhawk44]

I went and shot my M14 a couple weeks ago and noticed some opening of groups from it.  Shooting about 4MOA with handloads that have historically been 1.5MOA from prone.

Looking at the rifle, I found that the flash hider and front sight had developed some visible and audible wobble.

Phil Arrington had previously secured some wobble in the front sight in the past for this rifle, and his solution was red locktite.  I took the flash hider off using only my hands (once I took the set-screw out of the castle nut), so obviously the red locktite solution is not a long term one.

Messing around with it, I tried to peen the flash hider grooved engagement surfaces where it mates with the external barrel grooves.  Couldn't get rid of all the wobble doing that.  I did some digging in my garage and found some white plumbers pipe thread tape.

I wrapped this around the barrel, BEHIND the threads that the castle nut uses to lock down the flash hider (on smooth metal essentially, but over the top of the flash hider barrel grooves).  Basically, I made the barrel diameter a few thousandths thicker, and the tape became filler-material for the grooves so that the flash hider engagement surfaces have more meat to bite on.  Once fully re-assembled, the tape is invisible and the sight is 100% rigid with no wobble at all.

Any reason why this plumber's tape solution might not be a good one?  Barrel temperature after strings of fire?  Unknown chemical reaction with the barrel? 

[AJ Dual]

The plumbers tape is just teflon so no problems with reactions, and it'll withstand pretty high temperatures.

The only issue with using it in this way is that it's soft. And the flash hider will still wobble, and the tape will grind down over time, leaving you loose again. Red loctite is probably a better answer since it at least lasted this long.

A crush washer might tighten things up, otherwise, you need a new flash hider with an I.D. of a thousandth or two less on its threads.

[Harold Tuttle]

degrease and red locktite

[kgbsquirrel]

Once you removed the stop-bolt were you able to turn the castle nut by hand? If so, sounds like it's way too loose. It's not to much the channels or the OD of the barrel at play here, but the shelf that the castle nut presses the flash hider against. The castle nut needs to be tightened down appropriately in order to firmly hold the flash hider against the shelf (and thus prevent it from wobbling). Do you have a set of castle nut pliers?

[dogmush]

I prefer, and we use in my shop, Permatex over Locktite products.

This is what I would use:
http://www.all-spec.com/products/Permatex/Tapes_and_Adhesives%7CAdhesives%7CADH-03/27005.html

Teflon tape is probably not going to last as long as your previous threadlocker did.  It will flex a fair amount.  There's always JB weld, or actual welding.  That'd fix it.

[AZRedhawk44]

I was also thinking of checking home depot for an appropriate crush washer to fit the OD of the barrel ahead of the threads as well as the ID of the flash suppressor castle nut window.  Starting to get a bit over-precise for home depot though, and a hardware specialist like Copper State Nut and Bolt would be better.  Good to know my idea wasn't out of line and someone else thought of it.

kgb:  I removed the entire setup by hand, aside from the stop-bolt (used an allen wrench for that obviously).

When re-attaching the castle nut, I tightened by hand until I could go no more, then finished the remainder of a 1/8 turn (just enough to get the next full castle nut recess in line with the stop-bolt) by gently tapping the castle nut windows with a punch and hammer.  I think I ended up needing to turn it about 5 degrees that way, was all.  No deformation of the castle nut.

The only issue with using it in this way is that it's soft. And the flash hider will still wobble, and the tape will grind down over time, leaving you loose again. Red loctite is probably a better answer since it at least lasted this long.

It has no wobble right now, so I guess it's a "good 'nuff" solution for now.  Definitely better than it was before.  At least a hundredth or two of an inch lateral wobble was visible and audible.  Being that it's soft, that means it must be somewhat elastic as well, meaning any give in it will end up attempting to return back to a center point.

Do you think I'll get better rigidity by tightening one notch further with castle nut pliers?  I'm willing to get some, but I have Walt Kuleck's M14 book here next to me and it suggests to not overtighten the castle nut.

I'll ask the guys at Smith Enterprises about this problem next time I'm down that way, and see if their new manufacture flash hiders rectify this problem.

[kgbsquirrel]

I'll ask the guys at Smith Enterprises about this problem next time I'm down that way, and see if their new manufacture flash hiders rectify this problem.

That's always a good plan. I've purchased some stuff from them before and was quite pleased.

Also yes, as far as I understand it, finger tighten till stop, then proceed to the next available notch. When I first removed my castle nut on the other hand, from the factory it was so tight that it required some deformation of the castle nut to remove (same punch method as yours). I've not had any wobble issues after reinstalling it though, no locktite or other shimming methods used. A fresh castle nut and set of pliers are on my to-purchase-someday list.