277 Fury Pressure and modern components - WAS: Impact of shoulder vs nut on strength/max pressure capacity

cohunt said:

I wonder about longevity of bolt lug/action interface/contact area

I know that in the past there were some issues with titanium bolt/actions where some people had recorded increasing head space issues due to lug/action lock up area "stretching" on cartridges with larger bolt faces ( higher bolt thrust numbers)

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Not "in the past" AFAIK, still holds. Not a metallurgist, but this is my understanding...Ti is strong, but soft and gummy. Good strength, but doesn't have the same Rockwell hardness you need for high round counts esp with large casehead diameters/bolt thrust- hence the lug setback.

This is why you see them on low-round count mountain hunting rifles, and (generally) not target/PRS applications. Weight savings is the only advantage of Ti. Hardness, toughness, tensile strength all go to steel.

It would 'seem' then that the 2 primary considerations for the Fury with the hybrid case are:

1. Action that can handle the bolt thrust
2. Barrel radial strength that can handle the pressure

Anyone know where to find or how to calculate #2 based on material and diameter?

nkyshooter said:

It would 'seem' then that the 2 primary considerations for the Fury with the hybrid case are:

1. Action that can handle the bolt thrust
2. Barrel radial strength that can handle the pressure

Anyone know where to find or how to calculate #2 based on material and diameter?

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It's a hoop stress calculation.

^^^^ Exactly what I said in post #28.

If you search "Hoop Stress Calculation" you'll find how to do that. It is a common enough Engineering calculation that it is well documented. Most of the calculators out there are designed for use with thin shells and a barrel is too thick. Likely have to first find the formula for a thick shell and crunch the numbers yourself.

Thx GLZ ... I'm not a mechE so it's Greek to me...

Do you know how to calculate it for a 1.058 416 stainless barrel?

What thread pitch is the barrel? I doubt that it is Ø1.058" where it matters.

Then look up the material properties for 416 SS on matweb.com

Based on my qwik run-thru using guessed-at dimensions I'm finding that 100,000 psi is getting close to the YTS of 416 SS. There's still some margin, but not if a Factor of Safety is going to be used. For sure it won't handle 200,000 psi.

ntsqd said:

What thread pitch is the barrel? I doubt that it is Ø1.058" where it matters.

Then look up the material properties for 416 SS on matweb.com

Based on my qwik run-thru using guessed-at dimensions I'm finding that 100,000 psi is getting close to the YTS of 416 SS. There's still some margin, but not if a Factor of Safety is going to be used. For sure it won't handle 200,000 psi.

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I mentioned hoop stress in post 5. Yes I can do the calculations but won't. This is akin to telling you my handloads are a little hot but will work fine in your gun.
Sorry for that, there are online calculators and material properties data all over the web. Tread lightly if you don't understand the variables.

I'm not the one asking the questions, and I'm not going to do the calcs in public either. In #28 I pointed out that Hoop Stress had already been suggested.

ntsqd said:

What thread pitch is the barrel? I doubt that it is Ø1.058" where it matters.

Then look up the material properties for 416 SS on matweb.com

Based on my qwik run-thru using guessed-at dimensions I'm finding that 100,000 psi is getting close to the YTS of 416 SS. There's still some margin, but not if a Factor of Safety is going to be used. For sure it won't handle 200,000 psi.

Click to expand...

The 1.058 diameter I specified is typical for a small shank (savage) barrel nut setup. It would be larger for a shouldered setup. However, for most all actions it will be near that in the threaded portion of the barrel between the breech and the shoulder. This was the reason for my original title regarding strength impact of barrel nut vs shouldered setup.

My understanding is developing - thanks to all of you - I do appreciate it.

What I am coming away with is:

- A modern bolt action in good condition should be fine to handle the bolt thrust
- A barrel will be 'better off' if it is shouldered vs barrel nut setup (from a strength/pressure capacity perspective)
- The diameter at chamber/throat and the material the barrel is made of will impact how much pressure it can handle
- The pressure capacity can be calculated via hoop stress analysis and should be cut in half for safety margin
- Understandably, people who know how to calculate it are reluctant to do so for others due to potential impact of risk becoming realized - just like with handload data, etc

I suppose my quest now is:
1. Come up to speed on hoop analysis
2. Find out what barrel material will yield 160,000psi capacity or higher (to provide safety margin for operating at up to 80k psi)
3. What diameter will be required of that material and will it require shouldered setup or can it achieve that with a smaller diameter barrel nut setup.

For those of you that know materials - from materials in use by barrel makers, do you know who is using the strongest material and what that material is?

Thanks for all the great discussion ...

Ø1.058" will be the Major diameter of the threads. That means nothing, it is the Minor diameter of the threads that is important. The reason why is because the Minor diameter is the largest 'continuous diameter'. The Major diameter is discontinuous because it is interrupted by the "valleys" that are the thread itself. The Minor diameter of the threads is partly determined by the thread pitch. There won't be much difference between a 20 pitch and a 16 pitch on this Major diameter, but there is a difference.

I've seen nothing to support a conclusion that a shouldered barrel is stronger. Or weaker.

Just like your teachers didn't do your homework for you, I'm not going to do the Hoop Stress calculation in public. It is not a matter of liability. With the calculators out there this is not a hard thing to do. Getting everything into the correct units, and then converting the results back into units that you understand will be the hardest part. Suggest finding Joshua Madison's "Convert" utility. It's tiny and can live directly on your desktop. Dumb fone users are on their own, no idea how or if it can be made to work for them.

PSI in the chamber is not exactly the same as PSI in material strength. The units are the same, and that is a source of confusion, but 80,000 psi chamber pressure does not mean that a steel rated for 160ksi YTS is what is needed to have a FoS of 2.0 It is unfortunately not that simple.