I posted this question in "build it yourself" and got some responses I wanted to confirm.

I am installing my PRI tube on my new A3 upper, even with the 3 times 30 ft/lb torque routine I need about 90-95 ft/lb to reach the next hole, the previous hole only gives me about 20 ft/lb torquing.

Recommendations were as follows:
(1): toss the TM instructions and torque to next hole above 30 ft/lb. ie about 95 ft/lb in my case.
(2): Delicately and slowly remove some material from the face of the upper which is contacting the extension lip/stop.
(3): Change either the nut or upper to get a different threading relationship.

(1) (2) (3) or other ???

Guidance wanted
Thanks

when i installed my armalite tube they said 50lbs so thats what i did and it lined right up what does pri say maybe shoot them an email

Thanks Mcad, the 50 ft/lb sounds like a perfect condition setting. The TM manual says 30-80 ft/lb. Before installing the barrel on my new upper I practiced on my old Colt upper, I had no problem torquing within the 30-80 range.

I do believe that I have a worst case thread combination with my 2 parts.

Has anyone torqued their nut @ 95 ft/lb without problems or do I have to somehow reduce this torquing either by changing parts or lapping ??

Thanks

Solutions as I see them:

(2) would be my first choice, and get it to align in the 45-60 range.

(1) would be my second (hey, whatever works)
If you already torqued to 95, too late now.  No use doing anything else.

(3) are you kidding??? with a perfectly good receiver and nut that just need a little persuading?

Edited to add:  Expecting the nut to align with some magic torque spec is just asking too much... it just won't happen in the real world.

Don't torque the barrel above 80.  Essentially, torquing is unnecessary, just [b]tighten[/b] to the first hole where the gas tube will align.  25 is fine, 30 is better.

-- Chuck

Guys, I already torqued it up to 90, then removed the nut, I wanted to see how much more after 80 would be required without going too much over. Having done this could I have damaged the threads ??

Not to drag this thread on, but, I want a reliable rifle, so if I hand tight the nut then tighten to next hole I am about at 20-25, is 20 too loose ?? I have been considering removing some material, to at least got it above 30, but from what I have read I may be wasting my time.

My dileama is I feel 20 is too loose and 90 too tight...

okay, If I was in your situation this is what I would do.

I would carefully remove the finish only from the upper receiver (lap smoothing as suggested in the other post). Install barrel try to get close to 80 fps.

Test fire.

Stinger - Many have said toss the manual and tighten to next hole, but from which reference point. Is it next hole after hand tight (in my case 15 ft/lb) or is it next hole after the 30 ft/lb lower limit (in my case ~90 ft/lb) ????? [whacko]

[edited to add] I re-tried my barrel install and the hole 15 ft/lb (previously though to be 20-25 ft/lb) is just a bit more than hand tight.

Stinger, see above, NOTHING you do to the receiver has any effect on headspace.  NOTHING you do in installing a barrel has any effect on headspace.  Torque of the barrel nut has nothing to do with the headspace.  Only the barrel, extension, and bolt affect headspace.

If it aligns at 25, fine, but you have it at 90?  Now that you have it aligned there, it would not be good to loosen to 25.  Leave it alone, install the gas tube and go shoot.

When choppin on parts, always consider modifing the least expensive/hard to get one first.
SInce not all barrel nuts are created equal, a second barrel nut might give you a better tighness vs torque combo.
On many ocasions in my past, I did not have the luxury of a box full of barrel nuts to choose from however, especially since they were semi-permanently assembled to a barrel assembly.
So on more than one ocasion after torqing to the maximum threshold I was comfortable with, I marked the "rib" that would block the gas tube, and filed it off.
This makes no difference to the gas tube as it is still supported by the hole through the upper receiver.  The only down side is if you ever use this barrel nut on a different upper, because chances are this filed area won't line up for the gas tube.  But so what?  In other words, you could remove all but three of the the barrel nut's ribs and still wrench it on and off.
I am not sure if this will work on a PRI nut because I have never seen one, but it works on GI barrel nuts.
ColdBlue sends...

Just make sure that you haven't sheered of the extension index pin.

This can happen sometimes, and it will make the weapon difficult or impossible to zero in windage.

Calvin

Coldblue has a practical and easy solution.  I see nothing wrong with it, some purists get upset with this.

Vapor Trail:  This is why I advocate use of an action block, not barrel vise jaws.  You will not hurt the indexing pin or receiver slot if you use the action block.

Free Man

I definatly agree. Vice blocks should be used for FH/ MB or sight base installation only.

Calvin

Coldblue's solution is excellent although it might not apply to the PRI.

I HAVE messed up the indexing pin using an action block. This was on a barrel that had the same problem as Furet. I torqued it too much went to test fire and the windage was waaaaay off. If I would have torqued it to spec, filed of a nub and intalled gas tube everthing would have been just fine.

That was the first barrel I did. The rest have went fine without any problems.

Hey guys. Actually concerning the PRI barrel nut you can't file of a nub because the barrel nut is a solid piece with holes drilled through, even if I cut the metal between two holes the forend tub has two indexing pins that fit into the 3 & 9 o'clock holes in the barrel nut, so the nut must present a hole at the 12 o'clock for proper forend alignment. Good idea though...

As I see it from all your responses, I have 4 choices.

1- Hand tight + a bit more, to about 20 ft/lb
2- Torque to about 90-95 ft/lb
3- Remove 0.001 to 0.002 inches off the front of receiver threads.
4- Replace my upper, it is the most expensive piece but it is the only one I can get easily.

As of yesterday, I used option (1). If I use option (2) or (3) and things go bad, worst case scenario I will be forced to use option (4).

Thanks for all the replies, I would of thought a clean cut answer would have come out of this thread, but many have different technics and mind set about "torquing" issues. Makes for a nice debat, [:)]

Thanks to all for your ideas, I don't want to insult anyone by using someone elses idea. I think everyone is right in their own way. Having done business with Paul @ MSTN in the past I wanted to ask his opinion, but not having any new business to give them (thanks to the STATE department) I was reluctant to ask his advice, but I decided to anyway. I wanted to pass on the reply for everyones benefit.

Quoting Paul:
According to Colt, they will torque up to 150 ft lbs, so 90-95 is not probably going to hurt anything.  That said, we will typically swap barrel nuts if we get one that won't line up between 35-80 ft pounds.  Spec procedure is to torque to 35 lbs and loosen three times, then torque to alignment position.  Often times backing off several times will condition the threads so that they will go into the correct spot without excessive torque.
-end quote

So I guess really everybody is right with tightning to next hole, cause all setups should be well below 150 ft/lb anyway.

A credit goes to MSTN for their professional service - Thanks Paul

Thanks to all.... [headbang]

[sleep] Speach over...

Could we please end this thread........'nuf said on this topic!