M4 barrel nut torque specs?

[khc3]

I was reading the Colt M4 article in the most recent American Rifleman, and it said the barrel nut torque specs for the M4 had been changed from the spec for the M16.

What's that all about?

Thanks in advance.

[Robb Jensen]

I use 35-80ft lbs.

[Quib]

http://generalcartridge.net/Documents/TM9-1005-319-23.pdf

[40Arpent]

I use 35-80ft lbs.


Excuse me if I am reading you wrong, but 35 to 80 is a huge variation, no? What factors are considered when deciding what part of that range to go with? Just trying to learn...

thanks,

Pete

[MisterWilson]

Excuse me if I am reading you wrong, but 35 to 80 is a huge variation, no? What factors are considered when deciding what part of that range to go with? Just trying to learn...

thanks,

Pete

Torque it to 30. Then bring it to the next notch, but without passing 80lbs.

[Iraqgunz]

Because not all barrels and barrels nuts will thread on and line up exactly the same way everytime. Remember that the barrel nut has to line up right to insert the gas tube. I have personally never used a torque wrench when installing a barrel and I have never had one come loose either.


Excuse me if I am reading you wrong, but 35 to 80 is a huge variation, no? What factors are considered when deciding what part of that range to go with? Just trying to learn...

thanks,

Pete

[Quib]

Just trying to learn...

thanks,

Pete

And this is why I provided the link above to the -23&P. Read through the procedure for installing a barrel, and things should make more sense. ;)

[khc3]

So the article was wrong, and the specs for both the M16 and M4 have never changed?

[Iraqgunz]

I just looked at the article you spoke of and read that tidbit about the barrel nut. I then checked my M16A1 manual and it also shows 30-80 ft-lbs.

My guess is that it was a change that was instituted before being released which means that someone at Colt has that answer.


So the article was wrong, and the specs for both the M16 and M4 have never changed?

[khc3]

I just looked at the article you spoke of and read that tidbit about the barrel nut. I then checked my M16A1 manual and it also shows 30-80 ft-lbs.

My guess is that it was a change that was instituted before being released which means that someone at Colt has that answer.

Interesting, I wonder if that is the case with the described "improvement" in the "surface finish of the chamber."

I had never heard of either change so it probably is proprietary info.

[5pins]

I seem to remember there was a change, I think it was 35 to 75 but I’m not sure. The change must of came some time after I got out in 88.

[40Arpent]

Thanks to those that responded to my question, much appreciated! And apologies to the OP for slumming your thread. ;)

-Pete

[WpnsMan]

There isn't any change,

At least not as far as Rock Island is concerned. The old 319-23P was finally updated after 8 changes to the current one dated Nov 2008. As of Jun 09's ETM there have been no changes to it.

I.E., the torque spec is still 30-80 ft-lbs for all versions.

WpnsMan

[bkb0000]

I have personally never used a torque wrench when installing a barrel and I have never had one come loose either.

are you not concerned about over torquing? what do you do when it seems like its taking too much weight to line up?

[MisterWilson]

are you not concerned about over torquing? what do you do when it seems like its taking too much weight to line up?

Back off and try again.

[bkb0000]

Back off and try again.

and then what?

i've had a few bbl nuts that wouldnt line up under 80ftlbs.. i'll just try a different nut, generally. but once i establish im using more muscle than i'm comfortable with, i'll switch to a torque wrench to make sure i'm not going over 80.

in fact, i just had one a couple weeks ago that i had to dremel, for the first time ever- it was a receiver swap on a bushmaster 5.5" permed 11.5" barrel, so i couldn't try a different bbl nut without destroying the big ass MD. wasnt lining up, after working it for about 5 minutes, so i broke out the torque wrench to make sure i wasn't gonna dethread the new upper.. taking it to 85 almost got it, but i finally busted out the dremel and ground off the offending spur, rather than risk it.

[Surf]

As of my last Colt re-cert 2 years ago the Colt spec was 30-80 ftlbs.

I use 35 ftlbs then go to the next notch to align for the gas tube, which generally comes in within the upper range.

On a barrel nut that is used for free floats without notches (Daniel Defense etc), I tend to use 70ftlbs.

[Quib]

The trick to barrel nut alignment is called out in the -23&P, and that would be the use of grease on the threads of the upper receiver and the “3X torque” procedure.

The “3X torque” procedure might not always line up the gas tube at exactly 3X, but the reasoning behind the procedure is to progressively mate the threads of the upper, with those of the barrel nut.

Often times it takes more than the 3 tighten/loosen sequences to achieve barrel nut alignment. But using the tighten/loosen procedure along with adequate grease has always provided good results for me personally.

[Iraqgunz]

I really haven't had that issue. There was one or two instances out of all the rebarrels that I have done (both were Shrubmasters) and I simply used a different barrel nut. I use anti-seize on the threads and I do the 3x technique which has almost always worked out.


and then what?

i've had a few bbl nuts that wouldnt line up under 80ftlbs.. i'll just try a different nut, generally. but once i establish im using more muscle than i'm comfortable with, i'll switch to a torque wrench to make sure i'm not going over 80.

in fact, i just had one a couple weeks ago that i had to dremel, for the first time ever- it was a receiver swap on a bushmaster 5.5" permed 11.5" barrel, so i couldn't try a different bbl nut without destroying the big ass MD. wasnt lining up, after working it for about 5 minutes, so i broke out the torque wrench to make sure i wasn't gonna dethread the new upper.. taking it to 85 almost got it, but i finally busted out the dremel and ground off the offending spur, rather than risk it.