instead of full length resizing or partial (shoulder bump) just put the brass without a bullet in it into your chamber then close the bolt. In other words use your rifles chamber and bolt to bump the shoulder back if needed. Do this on every reload so if the shoulder needs to be bumped back it will only be a small distance.

some time in the recent past, the brass case came from that chamber.....Why do we think it'll now bump even slightly the shoulder back.....it won't...

It's why some folks only neck size and that's to retain the new seated bullet....one maintains nearly perfect headspace and minimal working of the brass....

The case fits back in the chamber as it came out....but with a new primer and powder and bullet....there is no need to bump the shoulder back.

In theory, you would never need to size brass other than to hold the bullet, but in practice it doesn't work that way, all the time. Due to these factors; actions that tend to spring under load, like levers and rear lockers. Chambers are not always round, nor are bolt faces flat and true. Brass might not be as ductile as some others. So, in a perfect world, you can neck size only, or not size at all for single shots, but in a real world for serious hunting, you need to allow for all the variables.
And if you wanted to size your brass in your chamber, due to the ductility of brass, it won't work. It will just spring back; it has to be worked past it's memory point.

ah ha that answer makes sense.

quote:

Originally posted by dpcd:
In theory, you would never need to size brass other than to hold the bullet, but in practice it doesn't work that way, all the time. Due to these factors; actions that tend to spring under load, like levers and rear lockers. Chambers are not always round, nor are bolt faces flat and true. Brass might not be as ductile as some others. So, in a perfect world, you can neck size only, or not size at all for single shots, but in a real world for serious hunting, you need to allow for all the variables.
And if you wanted to size your brass in your chamber, due to the ductility of brass, it won't work. It will just spring back; it has to be worked past it's memory point.

Well explained and absolutely true.

It get's a little more complicated.

There are different head space methods for varying cases and calibers. On the shoulder is only one. There are rimmed cases, belted cases and rebated cases.

Lots of different dies too. Some 2 set. Some 3 set, some 4 set. And even a 5th die for separate crimping.

It shouldn't be necessary to full length resize cases each time if they were shot with
"reasonable" pressures that didn't stretched the cases. However, hunting loads must chamber smoothly without hanging up.

There are lots of case preparation tools. One really good, easy and fast is the Wilson cartridge case gauge. It's a cylinder cut to exacting length. You just stick a case in and if it slips in easily it's ok. There are grooves on each end. The case head and neck must fall/measure between these "too long/too short" ends.

Some dies will neck down the case, full length resize, decap and neck expand in one operation. The next die will seat the bullet and crimp.

The necks may stretch and need trimming. Using a dial caliper is another way of measuring.

Once the dies are set up and adjusted it's just too easy to run the cases through. It has to be done anyway so there isn't any point in chambering a case to attempt to set the shoulder back.

If fired cases chamber hard and need forceful bolt closing, take a close look at you powder charge. It's too hot. Needs to be backed down.

quote:

Chambers are not always round, nor are bolt faces flat and true.

Very true.

quote:

Originally posted by dpcd:
In theory, you would never need to size brass other than to hold the bullet, but in practice it doesn't work that way, all the time. Due to these factors; actions that tend to spring under load, like levers and rear lockers. Chambers are not always round, nor are bolt faces flat and true. Brass might not be as ductile as some others. So, in a perfect world, you can neck size only, or not size at all for single shots, but in a real world for serious hunting, you need to allow for all the variables.
And if you wanted to size your brass in your chamber, due to the ductility of brass, it won't work. It will just spring back; it has to be worked past it's memory point.

roger

The reason you cannot size a case in a rifle chamber is that the chamber size is slightly larger than the spec of the case! The chamber has to allow the case to expand just a bit so that the neck can release the bullet at the correct pressure.

If the chamber was a tight fit at the neck, the pressure would spike very high when the round is fired. It would also extrude the brass forward - leading to more frequent trimming.

Therefore you need to use a sizing die to bring the neck to a smaller dimension that will grip the bullet adequately.

Bumping the shoulder is a separate issue - depends on what kind of die you use. If you use a neck sizing die, you will need to also use a body die once in a while to bump the shoulder back. Regular firing in the same rifle will expand the case and just neck sizing the case will mean that at some stage the case is too tight in the chamber.

If you use a FL die to partial size / neck size - this will squeeze the case side and push the shoulder forward. You will need to adjust the die correctly to bump the shoulder back at the end of the stroke on the press. You will be working the brass a lot more - each time you size the brass, it squeezes the sides, pushes the shoulder forward and then bumps the shoulder back again to spec. This results in brass flowing forward and the neck walls getting thicker. Some cases form a donut ring at the bottom of the neck.