Adjusting neck tension when using mandrels

[Bc'z]

With a quality seating die your bullet is the mandrel, set your interference with your bushing. Bushings DO size more than half the neck.
AS @JFrank said earlier use the appropriate bushing that your target tells you to use.
I anneal after every firing which equates to the brass being moved 3 times, once in sizing, once in seating, once at firing.
Shit next thing ya know someone will come up with a second anneal after sizing. Lmao

 

[Straightshooter1]

I figured I’d get roasted for the last post.

Sometimes I just have to bight my tongue.

 

[DHD]

With a quality seating die your bullet is the mandrel, set your interference with your bushing. Bushings DO size more than half the neck.
AS @JFrank said earlier use the appropriate bushing that your target tells you to use.
I anneal after every firing which equates to the brass being moved 3 times, once in sizing, once in seating, once at firing.
Shit next thing ya know someone will come up with a second anneal after sizing. Lmao

But actually, the second anneal does relieve the latent stress that was not relieved during the initial anneal.

Anneal, size, undersized mandrel, anneal, correct sized mandrel to final size and to smooth the ID.

Yeah, no...but what if. We might be on to something here. This sounds almost as much fun as bullet pointing (I pointed 500 Berger 108's yesterday and I am still suffering the mental strain and morning drinking isn't really a thing for me).

 

[Rick300]

I would buy a pin gauge and make my own.

I don't get why more people don't do this. Super easy and readily available

 

[Bronsin]

Neck Tension matters where it matters, on the target.

 

[Rich S]

I use a Porter Precision mandrel die. You can buy standard pin gages cheap on 0.0005 increments. The collets for different calibers are also inexpensive. Just grind a taper on it and you’re good to go. You can also use a collet bullet puller in place of the Porter die.

My preferred method is to use a bushing or FL die to size the neck about 0.0015 to 0.002 under the desired size then expand back up with a mandrel. I use imperial dry film in the necks before I expand them. I leave the mandrel die slightly loose. I anneal after each firing and have never had an issue with necks.

 

[goosepilot]

I would not think you would get more neck tension either
I ran an experiment last night to proof my theory on this
Posted here:

Does the bullet slide out of the neck or does the neck open to release it?

Primer fires, some powder burns, making gas. The gas pushes the remaining 2/3 powder forward, against the bullets base. It continues to burn till it consumed. Burn rate makes a difference. Slow powders may exit the muzzle, unburnt. https://discover.dtic.mil/

forum.accurateshooter.com

Thanks for the link.

After reading that thread I guess I have a stronger desire to set neck tension and to do it with a mandrel vs just a bushing.

I feel like if you don't turn necks it's even more important to use a mandrel.

 

[goosepilot]

What I used the pull gage for at the time was to accurately determine peak force needed to pull a bullet in order to compare that to the peak force required to seat the bullet; pulling force was about 2/3 the seating seating force. Knowing the cross-sectional area of the bullet, it was easy enough to calculate the pressure require inside the case to pop the bullet out. When compared to the maximum pressure for 6.5 Creedmoor, 63000-ish psi, it was negligible and not readily identifiable on a QuickLoad pressure graph where projectile travel is shown on the X-axis. IIRC, it would take about 550 psi to pop a bullet from the cartridge.

This led me to believe that while there are many good reasons to have neck tension, such as ensuring cartridges stay intact bouncing around in a box, or getting banged around in a magazine etc., and keeping the bullet pointed coaxially to the throat and rifling, I have my doubts that it has much effect on building the pressure curve.

View attachment 1647266

Interesting test, however in my mind it doesn't translate to what goes on in a chamber when it's fired. There's more going on than a simple push vs pull. That pulling force difference might seen small, but I think it's a significant factor when it's retarding an explosion for a fraction of a nanosecond

 

[Chris Edmondson]

Interesting test, however in my mind it doesn't translate to what goes on in a chamber when it's fired. There's more going on than a simple push vs pull. That pulling force difference might seen small, but I think it's a significant factor when it's retarding an explosion for a fraction of a nanosecond

If only we knew what happens when things go bang .

When it comes to neck tension, I think it's bounded by a range where not enough means the bullet is likely to change axial or radial position within the case after seating, and too much where the seating stem is engraving or damaging the bullet's jacket, or it's core when seated.

The best I can do is try to find a neck tension value which the target indicates is optimum, then endeavor to have all my necks sized to that value.