What is your approach to selecting a bushing size for a bushing die?
I have measured fired casings and new commercial loads to determine before and after neck diameters.
Clearly new cartridges vary by manufacturer,
I assume this ties to brass dimensions and tooling.

How do you determine your what bushing to use (there is a range for each caliber)

Clearly oversizing works the brass more and may create more neck tension than is desired...

Tell us,a bit about your process.

Thx

Fired cases tell you nothing about which bushing you want. The number you first need to know is the outside diameter of a loaded neck in the brass you will be using. Decide how much of an interference fit you want and subtract that.

Example: I've turned the necks of some Lapua 308 Winchester brass to .014" thickness. Twice that plus a .308" bullet adds up to .336". Suppose I want a .002" interference fit when seating a bullet. Then a .334" bushing will do the trick. (Assuming brass with necks that aren't work hardened and springing back)

I only use a bushing die for a .308, and set it up as follows:

1. Measure the neck O.D. of a loaded round with the brass you are sizing.
2. Subtract the amount of neck tension desired from the measurement above. I use .002 for single loading but you may want more for magazine feeding. This is the bushing ID to use.

If your fired case neck O.D, is much larger than the desired final neck O.D. you may need to size down in steps with two bushings to reduce run out. I use a lee collet die to start the sizing and deprime, then tumble and set the shoulder back .0015 with the bushing die doing the final neck down.. With uniform brass like Lapua, you can get by without neck turning or the expander on the decapping rod.
I just spot check 10 loaded rounds from the dies that have now loaded 4000 rounds since set up and the worst run out was .001" measured on the ogive.

I'm sure there are many other ways to do this, but this has worked well for me. BSA may be along shortly to tell us we should not be using bushing dies... grin.

Mathman types quicker than me!

https://www.youtube.com/watch?v=303zR8kspmY


I would watch all of his reloading videos.

Thanks all.
Mathman,
My thought on measuring OD of fired cases is that it tells me (& tell me if I am wrong) the approximate dimension of the neck of the chamber.

Since I am gauging precision right now I am thinking it is best to keep next tension to the minimum required for the job at this point.
I also understand that it is best not to overwork the brass..

Am I correct in assuming that the 0.002 - 0.005 range in loaded commercial rounds is largely due to brass wall thickness variation? I measured five rounds out of each of
9 different boxes, by 5 different makers and 3 different weights. The measurements were consistent for any given box. Typically consistent between two boxes by a manufacturer except where one box had crimped necks (which were 0.002 smaller than the same manufacturers unscripted necks)

Thanks

You can tell the chamber neck is at least as large as the fired brass neck. It will be somewhat larger.

That still has nothing to do with bushing selection.

I'm not sure of the desired neck tension which is better. I'm sure factory ammo has more than is needed for liability . I've been told hunting ammo you should have .005 , some videos say .003 and some people want .002. I try for .003 tension and has served me well.
As Mike stated about Lapua brass, I remove the expander and decap with a separate decapping die.

Thanks Mathman.

Rem,
Videos just spin and never start for me..

Visit Panhandle Precision on youtube.

Ach...
Stupid me.
There it is in the instructions...

Seems my caliper ID prongs(?) Are not so precise on a curved surface...
Below a certain ID the offset of the two blades(?), prongs(?) seem to interfere...

My old vernier calipers seem to do a better job on ID measurements...even if I use the digital caliper OD prongs on the vernier since it is so hard to see those little increments....

Thanks all

What are you doing measuring inside?

Wall thickness (by subtraction)
And,
Checking a hardware store bushing I use to standardize shoulder measurements.
Digital caliper was coming back wit .336 but it slid easily over the neck of something measuring 0.339 with the outside jaws...

Vernier gave 0.342 (converted and confirmed with digital by measuring outside of the vernier ) which makes more sense.

Clearly the design of the jaws matters....

Tube mic for wall thickness

Ball micrometer works well!

Meant to stop and pick one up at a place I know that has a few good used ones but I am far and away from there now...

Almost did get one years ago, before I had a use for it...
Shoulda succumbed to the whim I suppose.

Interestingly test fitting the bushing on the commercial loaded rounds it seems my measurements of diameter don't necessarily correspond to a snug fit of the bushing...
Maybe it didn't do enough rotate measurements or the crimp style effectively increases diameter...