I do consider tension as very important. Not just neck tension, but chambered body tensions as well.
Let me clarify my context of 'tension':
We often refer to bullet interference fit as tension,
We might consider seating force as indication of tension,
A few could consider neck tension as that caused by runout of a chambered cartridge,
So the term is pretty broad, but chosen context can hold well enough for subject discussions.
Much like 'annealing'. It's just easier to say annealing, while we really maintain a context of process annealing(stress relieving) -rather than full annealing.
I use 'tension' broadly, but this is what I'm generalizing in it;
A force to overcome on releasing a bullet is GRIP.
A force to overcome on seating a bullet is FRICTION.
A force that comes to new balance on firing is TENSION.
Bullet Grip = Neck Springback
No matter how much interference fit, or how much friction you provide to a seating bullet, grip is still just neck springback from last yielded to dimension over the area applied. It's a variance,, it's limited in adjustment,, but it can have an affect to tune, especially when best seated distance is off the lands, or when you're relying on an underbore cartridge at a very high pressure node(fast powders).
Consistent grip = management of springback
Seating Force = Friction(Kinetic)
Resultant friction coefficients of the bullet jacket and inner neck, and the force provided by neck tensile strength from the area of interference.
Seating force is not a direct indicator of resultant bullet grip and can be deceiving as applied(if not careful). A fully annealed neck, unexpanded, and squeaky clean inside, can provide seating with ~normal force, yet it has little springback to grip a bullet.
Variance in seating force causes changes in seating depths due to varied wedging of seater stems on bullet ogives.
Consistent seating depths = management of friction
Tension = perpendicular preloadings of chambered cartridges
When you chamber a banana, you preload it in abstract ways. On firing, the banana straightens but where is the bullet and where is it pointing while this is happening? Will this happen the same shot to shot?
This is where TIR comes in for tighter chambers, while more forgiven with looser chambers.
Why not just go with loose chambers then?
Loose chambers mean greater brass yielding to larger diameters, which means less recovery from thinner brass, leading to difficult extraction unless sized more, to cause more yielding and work hardening, which changes springback, which changes case capacities with each reloading/trimming cycle, varying peak pressure curves, leading to more load tweaking, so more trips to the range, where Mrs.Jones frequents her teasing, and your wondering interest causes confrontation with Mr.Jones...
Don't go to jail with Mr.Jones...
Stop paying too much for loose chambers.
Run with the tightest chamber you can manage, given qualifiers, and make straighter ammo for it(the two go hand in hand).
I do measure seating forces of my necks, while pre-expanding with an instrumented mandrel. Because I manage springback and friction really well, my grip can be inferred from seating force. But I'm not actually measuring grip, and I'm not aware of any tool to do this today. There is about 30% of one in my garage that I need to finish some day..
I need to get off the internet someday..
