Barrel Threads - 16tpi vs 20tpi

[Phil3]

I was looking at some custom actions and noticed that depending on maker, they are either 16 threads per inch (Remington), or 20 (Savage). Any inherent pros and cons for either? Just curious.

I was looking at the Defiance Tenacity (20tpi) and BigHorn Origin (20tpi) actions.

Phil

 

[WayneShaw]

More 18TPI out there than 16 or 20.

 

[Dusty Stevens]

The reason for a 20 is to use savage barrels

 

[MarkInFolsom]

But from a mechanical standpoint, is one of the thread pitches better than the others, and if so, why?

 

[Phil3]

But from a mechanical standpoint, is one of the thread pitches better than the others, and if so, why?

My question too. There are tables and such for determining clamping force and such.

Some information.

https://www.eng-tips.com/viewthread.cfm?qid=72123

http://www.accuratescrew.com/thread-series/

 

[Dusty Stevens]

Torquing a barrel down the way we do on a rifle none is superior to the other. The 20tpi takes longer to screw on and is easier to damage the threads over a 16tpi

 

[raptor1ronin]

Torquing a barrel down the way we do on a rifle none is superior to the other. The 20tpi takes longer to screw on and is easier to damage the threads over a 16tpi

This might be a stupid questions but lets say you have a bolt sent back when they are making your action so that you have twin actions ( extra bolt because this person was using one action for two different calibers). You get it back and screw on your old barrel from action "A", and put it on action "B" which is Twin, but the thread index is off by a 1/4 turn will that change your head spacing. or is that based off bolt? Should you no go Gauge it?

 

[Delfuego]

This might be a stupid questions but lets say you have a bolt sent back when they are making your action so that you have twin actions ( extra bolt because this person was using one action for two different calibers). You get it back and screw on your old barrel from action "A", and put it on action "B" which is Twin, but the thread index is off by a 1/4 turn will that change your head spacing. or is that based off bolt? Should you no go Gauge it?

Depend on the action and the tolerances they use. My Bighorn Actions hold pretty tight tolerance, I can swap my barrels back and forth. With other actions you may not be able.

 

[Dusty Stevens]

Always verify

 

[riflewoman]

From an engineering perspective, finer threads tend to be stronger in tension. When you torque, you apply a tension preload. (NO, you cannot calculate it no matter what the “mathematician masquerading as an engineer” tells you.). In theory then, a finer thread allows for a higher preload to reduce the probability of the barrel loosening. So what does this mean?

The difference between 16 and 20 (or 18) is largely a designer’s preference. Not that much difference in lossening. Not enough to justify, IMO, the different thread pitch. Especially when it’s been proven that commercial barrels have been over-torqued for years.

 

[raptor1ronin]

Depend on the action and the tolerances they use. My Bighorn Actions hold pretty tight tolerance, I can swap my barrels back and forth. With other actions you may not be able.

They are defiance