Neck tension

[Tac-O]

Making a brass neck smaller does not make the tension on the bullet more, it is still the same as if it was only .002" smaller. What changes is the force used to push the case out an extra .002" if going to .004" interference.
This is where you are all losing what neck tension is.
An interference fit is just that, interference. A bearing may have .015"-.002" interference, it is designed to stop the outside carrier from moving in it's recess, bullet interference is to stop bullets moving in or out due to handling and especially going from a magazine into the breach.
My comp rifles, which do not get mag fed, utilise .0015" interference fit, it still takes the same amount of force to remove as does a bullet at .002", .003" & .004" interference in the SAME brass.
Now, if we crimp, this is a whole new thing and very different to interference fit because we are now holding that bullet back for many more milliseconds while the crimp is unfolding from/out of the cannelure.
This is why a lot of factory ammo is crimped, they can use less of a faster powder and still bump up ballistics because the crimp allows for very high start pressure that would otherwise not be there, and uniforms the burn, which is why many factory loads get very good ES/SD numbers.
Anyway, I have rambled on enough, and still haven't explained why it is perceived that heavier interference affects outcomes…

Cheers.

I've never messed with neck tension much. I've just used the expander ball or mandrel that I have and rolled with it. I did at one time use the Lee FCD on all my rounds, but discontinued it due to being an extra step and not really seeing any noticeable gains on the target from my bolt guns.

For example, my FL die takes my 30-284 brass neck OD down to 0.333. the neck walk thickness is around 0.0145-0.015. loaded neck diameter is 0.3375-0.338. the mandrel I use to expand the neck is 0.336-0.3365.

What "tension" would that be?

with that particular load, my 30 shot ES and SD was not good relative to what most people strive for. I have about 0.250 of bearing surface in the neck. I also always get sooted necks after firing. I have thought that maybe increasing the seating depth or using a smaller mandrel might get me better ES/SD. Or, using the Lee FCD.

is it worth a try? Also, is it likely that I'd see increased pressure for that given load trying a smaller mandrel or FCD?

 

[dfanonymous]

I agree that there's not much benefit past .004, but measuring your bullet and accounting for spring back of the neck, .004 is still what I would do for auto loading weapons being used for precision.

These numbers are measurable, and that's why these mandrel and bushing sizes exists.

That said, I wouldn't bring Eric into this. The guy likes stupid simple reloading, and I tend to agree with him. I also got more stuff to do in a day then to be jailed in the reloading room. As it relates to neck tension, I'm only looking at ES. So if you want to verify that rather than trust the chrono, yes, distance is a way to that.

 

[cajun]

Did he say neck tension in the video? Yes he did. That's why guys experiment with different bushing sizes and mandrels.

 

[cajun]

I will say finding the right powder is 90% of the battle for the combustion side.

 

[Carey Farmer]

My brass after annealing only has about .0015" spring back after bullet seating. So any "tension" (that is, case neck sizing down below bullet diameter) over .0015" in my annealed brass adds little gripping force - just a little extra yield strength from extra work hardening.

Before annealing, my once-fired brass has spring back of around .002".

Above numbers are based on case neck ID measurements using mandrels with .0005" increments, with case necks that (after firing) have been sized down .003" - .0035" under bullet diameter.

 

[Mike Matteson]

My brass after annealing only has about .0015" spring back after bullet seating. So any "tension" (that is, case neck sizing down below bullet diameter) over .0015" in my annealed brass adds little gripping force - just a little extra yield strength from extra work hardening.

Before annealing, my once-fired brass has spring back of around .002".

Above numbers are based on case neck ID measurements using mandrels with .0005" increments, with case necks that (after firing) have been sized down .003" - .0035" under bullet diameter.

Is this sizing before or after annealing?

 

[Phil Rizzo]

Making a brass neck smaller does not make the tension on the bullet more, it is still the same as if it was only .002" smaller. What changes is the force used to push the case out an extra .002" if going to .004" interference.
This is where you are all losing what neck tension is.
An interference fit is just that, interference. A bearing may have .015"-.002" interference, it is designed to stop the outside carrier from moving in it's recess, bullet interference is to stop bullets moving in or out due to handling and especially going from a magazine into the breach.
My comp rifles, which do not get mag fed, utilise .0015" interference fit, it still takes the same amount of force to remove as does a bullet at .002", .003" & .004" interference in the SAME brass.
Now, if we crimp, this is a whole new thing and very different to interference fit because we are now holding that bullet back for many more milliseconds while the crimp is unfolding from/out of the cannelure.
This is why a lot of factory ammo is crimped, they can use less of a faster powder and still bump up ballistics because the crimp allows for very high start pressure that would otherwise not be there, and uniforms the burn, which is why many factory loads get very good ES/SD numbers.
Anyway, I have rambled on enough, and still haven't explained why it is perceived that heavier interference affects outcomes…

Cheers.

Does this information assume all brass manufacturers use the same alloy and processes?
I'm wondering how a blanket statement can be made here.
Surely it's not all identical in the "elastic zone", and gives the same numbers according to manipulation on a stress/strain gauge, regardless of thickness, composition etc.?

If the primer pockets on one end handle pressure differently it seems there would be some difference in the way the neck responds to our squeezing and dilating.

 

[robert rex]

Making a brass neck smaller does not make the tension on the bullet more, it is still the same as if it was only .002" smaller. What changes is the force used to push the case out an extra .002" if going to .004" interference.
This is where you are all losing what neck tension is.
An interference fit is just that, interference. A bearing may have .015"-.002" interference, it is designed to stop the outside carrier from moving in it's recess, bullet interference is to stop bullets moving in or out due to handling and especially going from a magazine into the breach.
My comp rifles, which do not get mag fed, utilise .0015" interference fit, it still takes the same amount of force to remove as does a bullet at .002", .003" & .004" interference in the SAME brass.
Now, if we crimp, this is a whole new thing and very different to interference fit because we are now holding that bullet back for many more milliseconds while the crimp is unfolding from/out of the cannelure.
This is why a lot of factory ammo is crimped, they can use less of a faster powder and still bump up ballistics because the crimp allows for very high start pressure that would otherwise not be there, and uniforms the burn, which is why many factory loads get very good ES/SD numbers.
Anyway, I have rambled on enough, and still haven't explained why it is perceived that heavier interference affects outcomes…

Cheers.

Pick two pieces of annealed and turned brass. Full length size with a bushing that gives you .002 neck tension. Now use a bushing .004 smaller. Put them both in an inertia hammer, and the.002 will drop out with the first tap, the one .004 smaller will take four or five sharp blows to remove the bullet. That's more neck tension. Think of it like compression socks when you're an athlete.

 

[Mikecr]

1. Like MagnumManiac said, interference is NOT tension, as force is not expressed in inches.
2. Friction is independent and different from tension.
3. The interference in play applies differently within -vs- beyond seated bearing length.
4. The elasticity of our necks under hoop tension is around 1/2thou. The rest is yielding (beyond self recovery).

 

[Phil Rizzo]

so what changes the ES/SD when we use different combinations of bushings and mandrels?
what causes bullets to be harder to extract from the case, manually, with a .004 interference over a .002?

Use simpler terms for all the dumbasses you have surrounded yourself with, please.

 

[Huntnful]

I started using mandrels that are .0005 under bullet diameter for .001 "neck tension" theoretically. Everything seems to shoot better and easier. I may even start using a bullet diameter mandrel. I feel like consistent seating tension is more important than a specific tension. And it seems like the lighter I go, the more consistent the seating feels.

Just my personal experience though.

 

[MagnumManiac]

Pick two pieces of annealed and turned brass. Full length size with a bushing that gives you .002 neck tension. Now use a bushing .004 smaller. Put them both in an inertia hammer, and the.002 will drop out with the first tap, the one .004 smaller will take four or five sharp blows to remove the bullet. That's more neck tension. Think of it like compression socks when you're an athlete.

so what changes the ES/SD when we use different combinations of bushings and mandrels?
what causes bullets to be harder to extract from the case, manually, with a .004 interference over a .002?

Use simpler terms for all the dumbasses you have surrounded yourself with, please.

@robert rex
What you describe may be true in your brass, but generally speaking, it varies from brass to brass. Do you anneal? If the answer is no, then it is self explanatory, if the answer is yes, then the same applies.

@Phil Rizzo
The answer is that your brass and loading techniques requires that .004" to get the SAME results as 'tension' as other brass. All of this is not determined by how much you are moving the brass, but what HARDNESS your brass is. Does this make more sense to you?
Malleable brass has more tension than hard brass, as you can't measure hardness directly, you don't know how much interference is required to get the desired results.

Cheers.

 

[Phil Rizzo]

I've wondered if a certain minimum had to be achieved to get the best uniformity, regardless of the number .002-.003 or whatever.
I think you are telling me i've achieved that minimum when ES/SD is tight consistently.

So, when it's all said and done we are going to strive to use what interference yields us the tightest results, within reason.

Annealing, bushings, mandrels, ball and regular mics, Giraud 3way, I guess next stop is IDOD.

 

[Carey Farmer]

Is this sizing before or after annealing?

Yes, I size and clean (in a vibratory tumbler) before annealing. That makes sure there isn't any lube left inside the case neck when I seat the bullet.