stubborn barel nut-----AR

S

skizzums

New member
habe you seen a barrel nut like this? I haven't, great design, love that you only have to index the handgaurd and not the gas-tube like all the other free-floats I have done. also it uses an actual wrench rather than those little two pronged deals that every other free float nut has used in my past. but danged if I cannot get it off.....am I missing something? I have looked and looked for a set screw or anything that would make it so freaking tight. it's brand new, just assembled and arrived today, couldn't imagine a factory would loc-tite or anything like that, but even so, the weight I putting on this screw would break loc-tite I would think. suggestions please. sitting with penetrating right now, don't want to break out the torch and damage the finish on the upper

 
nevermind, just needed to grow a pair. but geez was that thing tight, I have never....
Click to expand...
Breaking torque on a PTAC upper that I tore down was 195 lb-ft. I nearly broke off a corner of my bench, trying to get that nut to let go.

No loc-tite. No sealant. No grease. But the threads did look slightly oiled before being annihilated by the gorilla torque.

I checked the upper in a few places with a straight edge, and it didn't appear to have suffered from the experience. I did, however, end up using that upper for a dedicated golf ball launcher (tied to a crappy 16" PTAC barrel).
 
this also had no grease, I was surprised to see that. couple hundred 's of torque sounds about right, my little 150 pound body literally jumping up an down on it with a lot of leverage, WTH?? I have had better times standing on 3" breaker bars and jumping on them to remove rusted lug nuts. this just didn't seem right, if it takes that much torque to line up the barrel nut, maybe I will remove a thousandth off the bottom, would that work?
 
I can't really offer any advice there, other than to say that I did have to lap the golf ball upper, in order to get a reasonable torque on the replacement nut. (Among others that I've lapped.)

And....


A standard barrel nut has 20 notches, each of which represents 18 degrees of rotation and 0.0027" of compression (nut to upper).

Your barrel nut has only the 6 flats, each representing 60 degrees of rotation and 0.009" of compression.
And, I assume, 12 sets of holes for handguard attachment.
If it's just the holes that must be indexed, then each set of holes represents 30 degrees or rotation and 0.0045" of compression.

I would probably get a basic torque on the nut to see where it fell, crank it up to 80 lb to see how far off I was, and run some numbers from there....

For example, if I was off by half of an index:
I wouldn't try to take all of that at once. I'd probably start by shooting for 1/3.
1/3 * 0.0045" = 0.0015" to be removed from the upper, barrel extension, or seating face of the nut.
Test.
Lap.
Test.
Torque.
 
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