M14 Forum

MemphisMachinists

Recently I saw a post from someone wanting to know about barrel shoulder crush and then last night there was a post about the reciever face alignmet.

Add some alcohol and sleep and I wake up thinking about all this. The reciever is so hard that It probably doesn't move much. Although I think if enough force is applied there could be an adverse effect on it. I have come to believe that you need just enough tourqe to keep the barrel from coming loose.

I have seen barrels with no undercut at the rear of the threads and some with one. There are square face shoulders and some with tapers.
I think from now on if possible I will cut a taper into the face of the barrel shoulder and give it some undercut at the end of the threads. This should give some actual crush to it rather than the stretching that likely takes place without these clearences.

The reciever face alignment comes into play (in my mind) because even if it is perfectly perpendicular to the base of the reciever/and the barrel threads of the reciever overtightning with no clearence could force the barrel to cant slightly.

I am not claiming any of this as fact. These are just my thoughts on this subject and am open to critisism and construtive ideas.

art luppino

All of those ideas are good, since you have the capacity to do the necessary mods [few do] please let all know how it works out..

Barrel torque has also been an interest to others for a number of reasons. Once the contact is made between the two components what exactly occurs is a mystery..

On my personal rifles.

Barrel installation is a long task. I try to relieve the barrel shoulder leaving between 10 and 12 degrees short TDC hand tight. The shoulder is cut square. Locking the barrel up with splines at TCD I add a small amount of oil to the threads that has mild valve grinding compound mixed in. Than I spin the receiver in and out gently until there is a "thunk" sound along with a hand feel of dead stop. Not rocket tech. but over the years one gets a feel for doing this.

All the oil and compound is remover, than I apply loctite, I think is is No. 721, very strong stuff. and spin it in again. Usually this requires a few taps with a dead blow hammer to align the receive to TDC.

To establish a TDC relationship between the two parts I use the flats on front and rear of the front sight mount and the narrow ledge behind the rear sight platform.

This method has never loosened or resulted in a barrel pointing off alignment. It is my guess, the heavy torque requirements suggested may have come about because of the possibilities of automatic firing...

I am not suggesting anybody else should use this method, or that it is fool proof, merely a disclaimer.

leadbug

Thanks for the thoughts and insight Art. I CAN'T WAIT to do this process the first time myself!

I tend to agree with both of you on keeping the torque to the minimum.

tokiwartooth

Get the Walter Kulek book. Invaluable.

MemphisMachinists

Had the opportunity to do two this weekend with Articdog. We turned the sholder back a bit on both of them and I undercut the area behind the threads slightly. We may have put a bit more than 80 ft lbs tourqe on them tighten them up, but not by much. I think they both worked out well.

I had an orportunity to use his badger alignment guages and at first I didn't think much of them, but after my thoughts have gel'd a bit I may get me some. I don't know if this is a common problem with them, but his needed some clearence added to the slits that fit over the rear sight ear thingies. I had not used these before and when I first put them on we checked it with an indicator just to see how straight his site base was. It was so far out I figured something was wrong. Upon closer inspection the guage was touching the inside of the site base on the sides (radius) before it got all the way down. I took a 64th thickness down an eighth on each side from his guage. When we reinslalled it and checked the top of the bar I think we only saw about .007" variation from one side to the other.