Opinions on spiralock threads.

[Roeder]

Well, some very good br smiths are using it on the male side. I don't see how it matters if its on the male or female side.

Can you give some examples of these very good br smiths?

 

[ebb]

Mikecr how does a Savage nut help? On a shoulder system you have a male and a female thread, with a barrel nut you have a male and TWO female threads. Actually the barrel threads, the male threads are used twice, once in the receiver and once in the barrel nut. So the barrel nut system will give twice as much loading and unloading.

 

[Outrider27]

Mikecr how does a Savage nut help? On a shoulder system you have a male and a female thread, with a barrel nut you have a male and TWO female threads. Actually the barrel threads, the male threads are used twice, once in the receiver and once in the barrel nut. So the barrel nut system will give twice as much loading and unloading.

Just as a point of reference, in a threaded joint (regardless of which of the two types we are discussing here it is), while the service environment puts stresses on the threads in the joint, including cyclic loads (as in the case at hand), there is no loading or unloading of the joint that increases or decreases the stresses on the threads in the joint UNLESS the load(s) applied by the service environment exceed the forces generated by the preload on the threads. IF the preload on the threads is exceeded by the cyclic forces imposed on the joint by the service environment, the joint is not properly designed and will fail in short order due to low cycle fatigue. (note that for low cycle fatigue failure, it is not necessary for the cyclic stresses to exceed the yield strength of either the male or female portions of the joint, the load must only exceed the preload applied to the joint, which is what makes low cycle fatigue insidious).

 

[mikecr]

I drew a pic of barrel nut action(with a crayon). You can see how the nut is pulling all threads together away from the boltface, increasing thread contact and in the correct direction given outward pressure of firing..

 

[mr45man]

I drew a pic of barrel nut action(with a crayon). You can see how the nut is pulling all threads together away from the boltface, increasing thread contact and in the correct direction given outward pressure of firing..

I would disagree with all of this? So there is no bolt thrust?
And how does the action whether there is a nut or the shoulder pulling the threads?
I am old guy just asking.
John H

 

[Dusty Stevens]

Im still trying to find a very good BR smith that uses this method. Ill keep looking.

 

[Scott Harris]

Talk to Greg Tannel. I looked into it but the threading inserts were very expensive and I did not pull the trigger. I can't remember if Greg is still using them.

 

[Scott Harris]

I drew a pic of barrel nut action(with a crayon). You can see how the nut is pulling all threads together away from the boltface, increasing thread contact and in the correct direction given outward pressure of firing..

You show the firing pressure only in one direction: pretty sure that's not correct. The bullet is getting pushed forward and there is an equal and opposite force pushing the bolt hard to the rear...you feel this force as recoil. It is pushing hard against the bolt face causing the same loosening effect between the barrel nut and action face that occurs with a standard setup. The barrel nut is simply and extension of the barrel and does not change a thing mechanically.

 

[gunsandgunsmithing]

It's easy enough to figure the clamping force generated by standard threads, but how much "unloading" force are we dealing with?

 

[mikecr]

The unloading force is pretty much the same firing force in all other directions.
After all, the bolt force is also applied to the barrel in the opposite direction.
That's what makes this mechanical connection different from normal. We're not just holding the barrel into the action(that's hand tight). Ideally, we're also producing a connection that remains exactly the same under actual load.

You can tighten the living hell out of standard threading, or you can consider specialized connection methods. Obviously both work.

 

[gunsandgunsmithing]

Just thinking here...but if the joint unloads, and you have a rh twist barrel, would it not tighten the barrel when fired? We all know this tightening happens to some degree...I'm just thinking about how it happens when the joint unloads, specifically. I would think it could add substantially to the barrel's torque value over time. Most of us have seen some barrels get really tight, too. As I said, just thinking out loud here. Seems a lot like how an impact screw driver works.