How tight is tight?????

[G.T.]

Hi Rich.... I've not tried to go much tighter then the 50 ft. lbs. as it seems to be plenty... But, on previous efforts, it was hard to gauge as my barrel vice on the taper was inconsistent from job to job.... Was the barrel that tight, or just barrel vice that loose?... Two things made this latest attempt possible, one was the straight, large constant diameter Bull Barrels.. And the other, was a special adaptor socket to fit over the end of the receiver blocks to attach a torque wrench..... I had the set up made about a year or so ago, when I first envisioned making a few barrels... seemed that a little info was lacking in my skill sets so I bought a Snap-on torque wrench, and Walla! We have usable info! ..... .. Best to all, til....lat'r....GT....

[Olle]

Like I have told GT in private conversations, I believe that many are making this more difficult than it really is. I work on Colt revolvers on a regular basis, and I have encountered factory installed barrels that were so loose that it only took a light tug on the wrench to get them off. Still, they had stayed put, despite the repeated beating from .357s and .44s.

When I do revolver barrels, I set them back to index by hand at about 10 o'clock, cut the crush area (about 50% or so) and torque them with a barrel vise and action wrench. They do "float" once they reach a certain torque, but that's the whole purpose of the crush area. They are easy to install and they don't come loose, and I would do a Luger barrel the same way.

Really, it's just a screw and there's nothing magic about it. I believe too much torque is more detrimental than too little.

[Dick Herman]

Ideally, the proper torque should set the barrel threads (any threads) in the elastic limits range of thread material. If the torque is too high the threads could be in the plastic (deformed) region or fail (stripped). Since the barrel has a slightly smaller (male, bolt) thread diameter, the failure would occur on the barrel first.

If the material properties and thread form dimensions are known, calculating of the torque limits is easy.

[Eugen]

I have a related question. Is antiseize use advised for those threads?

[Olle]

Originally Posted by Eugen

I have a related question. Is antiseize use advised for those threads?

Absolutely, especially if you're one of the believer in high torque. As the barrel is tightened, the surfaces are pressed against each other harder and harder, and without antiseize they can gall. This is a phenomenon that will make the surfaces stick to each other, and once that happens it won't go any further. You can't finish tightening it, and you'll have a hell of a time trying to unscrew it again. I use copper paste for this, it seems to have the best lubricity of the types I have tried.

[sheepherder]

Originally Posted by Eugen

I have a related question. Is antiseize use advised for those threads?

Some type of lube is required. You can't get a good torque reading (or 'feel') with dry threads. The friction requires additional pressure to overcome. I've used Nevr-Seize, wheel bearing grease, LSA, and presently am using white lithium based grease.

I stopped using Nevr-Seez (on firearms) because it is too messy. Seems like you can never clean up the excess.

[Dick Herman]

Galling is much like surface contact welding. If there is a difference in the hardness of the steel screw (barrel) and the steel nut (receiver) galling should not occur. However using a thread lubricant greatly reduces the chance of galling AND improves the torquing efficiency.

[Olle]

Originally Posted by Dick Herman

Galling is much like surface contact welding. If there is a difference in the hardness of the steel screw (barrel) and the steel nut (receiver) galling should not occur. However using a thread lubricant greatly reduces the chance of galling AND improves the torquing efficiency.

I'd say it's very much like contact welding. Also, the increased friction and pressure cause microscopic tears in the surface, which will make them so rough that they don't want to slide anymore. I believe this is what happens in friction welding as well, right before the material starts heating up.

I have had the questionable pleasure of seeing that happen, and I thought I would never get the barrel off again. The shiny contact surfaces on the shoulders were dull and torn, just like if the parts had been welded and then pulled part again.