Gunsmithing Stainless barrel/Titanium action - How much torque?

[SmokyJoe]

I have a Bartlein CF barrel and Fuzion Ti action to put together. Despite several hours of Google searches I am not seeing much in the way of torque recommendations for a titanium action. There is plenty of data and opinion on steel to steel, all the way from hand tight to 100 ft-lbs. As titanium is not as rigid, and softer than steel, I don’t want to over-torque and damage the action threads. I would appreciate hearing from anyone who has good guidance on this.

The tenon threads are 1-1/16“ x 16tpi. I will be using Permatex Nickel Anti-Seize. The action is 6AI-4V

I will check in with Lone Peak and the gunsmith who threaded the barrel and will post their info, but thought it might be good to hear from the hive as well.

 

[gnochi]

You won’t need to adjust the torque setting. Typical torques are far below what it would take to shear the threads or break off the tenon - by about a factor of 2 to start yielding threads - and 6AL-4V titanium has about 3x the yield strength of 416R stainless.

Just make sure to use your nickel anti-seize on both the threads and the shoulder.

 

[Mordamer]

With Titanium the standard torque procedure is pretty well known and require 2 steps:

1. Tighten until you hear the crack.
2. Back off a quarter turn.

Just kidding. Some of your assumptions are wrong about titanium. Your action is almost certainly made from Grade 5 titanium which has a yield strength north of 100 KSI. Most stainless steel actions are made from alloys that will be somewhere around 40 to 60 KSI for yield. Your titanium action is certainly not softer and weaker than a stainless action. However, titanium is known to gall badly as is stainless. I recommend you make sure the threads are coated in a thin layer of anti-seize compound. If it were mine I'd give it the full 100 FT-LB of torque and not blink an eye. You'd actually have to be at somewhere over 200 FT-LB before the barrel tennon got anywhere close to yield.

 

[E. Bryant]

If it were mine I'd give it the full 100 FT-LB of torque and not blink an eye. You'd actually have to be at somewhere over 200 FT-LB before the barrel tennon got anywhere close to yield.

You're way, way below the thread yield at any reasonably obtainable torque. Play around with a thread torque calculator (such as https://www.futek.com/bolttorque/american) and you can see that maximum torque values are north of 700 lb-ft. Good luck hitting that with a standard barrel vise and action wrench.

 

[BCX]

My Lone Peak TI Proof CF build was torqued at 100 FT LBS from a reputable smith.

 

[gnochi]

You're way, way below the thread yield at any reasonably obtainable torque. Play around with a thread torque calculator (such as https://www.futek.com/bolttorque/american) and you can see that maximum torque values are north of 700 lb-ft. Good luck hitting that with a standard barrel vise and action wrench.

You're actually limited by 3 threads of shear area yielding at the pitch diameter, not the tenon failing in tension. The number I napkin-mathed was about 250ft-lb. (Naturally the 3 threads thing isn’t quite right for mismatched elasticities, but it’s a decent do-not-exceed for ultra fine threads.)

IIRC the gorillas at Tikka and Marlin do about 200ft-lb factory.

 

[SmokyJoe]

With Titanium the standard torque procedure is pretty well known and require 2 steps:

1. Tighten until you hear the crack.
2. Back off a quarter turn.

I’ve done that, although I would back it off until it starts to bind up again, sort of engaging the back side of enough torque. As I do this I really focus on going back in time. AKA the Overunning First Base Rule; no prob, you’re still safe!

Thanks for the detail and for ending some of my illusions about titanium.

 

[Mordamer]

You're way, way below the thread yield at any reasonably obtainable torque. Play around with a thread torque calculator (such as https://www.futek.com/bolttorque/american) and you can see that maximum torque values are north of 700 lb-ft. Good luck hitting that with a standard barrel vise and action wrench.

Yeah, I've played with the calculators. For this application they are not accurate, but you are correct that most barrel vises would slip before you could ever apply enough torque to damage the tennon.

 

[RTH1800]

I have a Proof CF on a titanium Fuzion. .233 AI.
You are really going to like that rifle.

 

[LRI]

Grease it up with copper anti-seize and snug it to 100lbs.

 

[SmokyJoe]

Grease it up with copper anti-seize and snug it to 100lbs.

OK, so 100 ft-lbs it is. Any difference between copper and nickel anti seize for this application - SS/Titanium?

 

[RTH1800]

LRI assembled mine so I guess it is at 100 FP. Shoots great and is now my go to CF bolt gun.

 

[LRI]

OK, so 100 ft-lbs it is. Any difference between copper and nickel anti seize for this application - SS/Titanium?

I don't profess to know every possible detail on the products you are asking about. I just know that copper A.S. works.

 

[gnochi]

OK, so 100 ft-lbs it is. Any difference between copper and nickel anti seize for this application - SS/Titanium?

At elevated temperatures, copper can exacerbate fatigue cracking in stainless steel (which is why we don’t use copper AS in exhaust systems), but rifle barrels shouldn’t get hot enough to matter.

Nickel AS is slightly more expensive, but completely inert as far as firearms materials are concerned. If you only have one anti seize tube, make it nickel. If you’re using enough AS for the cost to actually matter, copper is fine.

 

[MagnumManiac]

I prefer nickel personally on stainless barrels/actions, but would use the same on Titanium.
I run 100lbs/ft only if the rifle is not a switch barrel, if it is a switch barrel, I run it hand tight then a very slight ‘nip’ up, maybe 10-20lbs/ft tops.

Cheers.

 

[SmokyJoe]

Again, thanks for all your input. Super helpful. I spoke with GAP, who chambered and threaded this barrel, and they, like LRI, torque these to 100 ft-lbs.