Neck tension question

[Shootin4fun]

I now anneal after every firing and guess what- no discernable difference in velocity between cases fired 4 times and those fired 10 times. (Lapua, 6.5cm 270 win 243 win). I still track batches though. But it means i can acually span 2 batches of different "generations" while testing loads and know that any differences are from changes in the load, not the fact that they were shot from different batches. I suffix batches with a letter, starting with A and progressing alphabetically. My M cases produce the same velocity as G cases with the same loads.

No turning, no expander ball, full size only, bushing die. (Abandoned neck sizing). Though for my BAR I do use the expander because necks sometimes get dented/deformed. When using an expander ball i lube the inside of the neck, then remove the lube with an isopropyl dampened cotton swab. The cases get beat up by automatic ejection process before primer pockets ever give way.

As most of us do, i seek single digit SDs, and get them on all rifles, even the BAR (270).

PS, and my neck walls do not seem to be thinning out at the M generation.

 

[lancetkenyon]

If you are going to use a "Sizing Die with Bushings" you really should be "Turning" the Necks to get a consistent wall thickness. Then you can use the correct Bushing for the neck tension you want.

While this is correct, it is not 100% necessary.

I HATE turning necks. With quality brass, it is less of a requirement.

I feel I get plenty accurate and consistent loads without this step.

 

[Csbc4fun]

I keep thinking i should learn about mandrels but ive been using standatd dies for over 50 years, and my SDs are in single digits, somtimes under 5, so im not sure if i would benefit from a whole changeover. If my stats are what i said, do you think i would gain any significant improvement by switching over? I don't plan to hnt over 600 -700 yards at this point but i do ring steel out to 1k.

Sounds like you are meeting your needs quite well. Mandrel does add one more step and you may not "Need " it to be 100% successful at meeting your goals. However, it is very easy to do and I wouldn't shy away from it. 21st Century web site has all the info you need. I use their mandrel 0.001" under my bullet size, with a window.

I didn't "Need" a Henderson trimmer either, but I sure enjoy using it!

 

[ntsqd]

The machinists here already know this, but I thought that I'd mention it for those haven't had any training on this.

You can't get an accurate ID measurement using calipers. This is because the ID jaws have a very small flat on them. That flat's corners touch down on the ID of the neck leaving a tiny air gap between them. That air gap times 2 is the error in measurement. It's small, but it's there and can be proven by using gauge pins to measure the ID of the neck. The pin that fits will not be the dimension that the calipers display. The error reduces in magnitude as the ID of what you're measuring increases. I've no idea of at what diameter it become noise, but I am pretty sure that none of us want to shoot a bore that big!

 

[lancetkenyon]

Who offers inside mandrels of different diameter for the same caliber? I use Sinclair mandrels, but these come in stated calibers only.

Sinclair also has "neck turning" mandrel, which are .001" smaller than their "expanding" mandrel.
Neck turning .261"
Expanding .262"

 

[QuietTexan]

Who offers inside mandrels of different diameter for the same caliber? I use Sinclair mandrels, but these come in stated calibers only.

21st Century
K+M
Porter Precision

 

[ntsqd]

If you use the Porter Precision system then you can order their pins or any other gauge pins in any size that you could possibly want. I sold off my Sinclair stuff to move to the Porter Precision system because gauge pins are made to a known gauge pin precision standard are available by .0005" increments from too small to be of use to this need out to something far larger than we'll ever need.

 

[Phil Rizzo]

When I find a way to do it that seems like I'm moving beyond a crawl, I'm going to start turning necks.
Just to knock off the high/thick spots.
New brass, one time, all done…?

 

[Bob Wright]

A pin gage is only a go/ no-go measurement
A ball mic is a wall thickness only
Calipers are not a reliable method of measuring wall or bore size.
If whatever you're doing for measurements and loading is getting good results, carry on. No argument here.
I don't see a need for anything more than what the community is doing or can afford.
Turning and reaming simultaneously is the best option but only when you have to. Two of my rifles have tight necks. I didn't get to pick the reamer print when ordering the chamber jobs.
So I turn and ream for just those. Once and done.

 

[Hugnot]

I go for a nice slip fit of bullet into fired brass- consistent neck tension With ammo that requires neck down to smaller ID neck turning is usually required, like .270 W to 6.5-06. .223 to .20P, 7X57 to 6mm Rem/AI. Annealing brass helps to reduce spring back and makes for more consistent neck tension. After neck down using F/L die with no expander I use a Lee collet die then turn necks so neck walls are .012-.013. After first firing I use a body die then the Lee Collet Die. If I don't get a nice slip fit, more turning, .001 increments. My chambers are reamed to allow selected bullets to be seated so the boat tail is above the shoulder junction. I anneal every 4 cycles.

A pic of an assembled 6 AI round made from 7X57 Mauser brass, cheap PPU.

 

[Dragoon300]

The machinists here already know this, but I thought that I'd mention it for those haven't had any training on this.

You can't get an accurate ID measurement using calipers. This is because the ID jaws have a very small flat on them. That flat's corners touch down on the ID of the neck leaving a tiny air gap between them. That air gap times 2 is the error in measurement. It's small, but it's there and can be proven by using gauge pins to measure the ID of the neck. The pin that fits will not be the dimension that the calipers display. The error reduces in magnitude as the ID of what you're measuring increases. I've no idea of at what diameter it become noise, but I am pretty sure that none of us want to shoot a bore that big!

Add to that your ability to "feel" the caliper and know when you are measuring correctly.

 

[Mikecr]

.015 + .015 + .284 = .314
Based on that I should be able to use a .312 neck bushing and achieve .002 neck tension.
Will this work?

This won't actually turn out exactly like that. There is spring back, the bushing result is affected by total sizing, neck thickening with downsizing.
But it likely does not matter with a .312 bushing as a reasonable beginning here.
It will work.

 

[Mike Matteson]

If you are going to use a "Sizing Die with Bushings" you really should be "Turning" the Necks to get a consistent wall thickness. Then you can use the correct Bushing for the neck tension you want.

That what's I was going to add.. I strongly feel that the case neck should be cut to even out the thickness of the neck. For release and annealing evenly. It may not be needed on the necks hitting the chamber wall unevenly. That may or may not cause a very small problem. When I finally get my reloading shack finish. I will see if there is any detectable difference in grouping. That will have to be done in one of my older rifles. All my newer rifles the neck chambering are reduced. The neck thickness has to be reduce to fit inside the chamber. This one of my reason to have my reamer made, and I get to keep them. I can rechamber my barrels the same. Instead of taking my barrels in years later to rechamber the barrel and get the same chamber. So I can finally get through my head what or which works better.

 

[Revolting Peasant]

Porter Precision Products.
Great guy making great products. His system allows you to get mandrels in just about any size you could need. Not just what the manufacturer thinks you need. If you want to experiment with neck tension and mandrels, this is the one.