Reloading (30.06 brass length question)

[glenn curnow]

Hi guys,

Just a question on reloading. I'm just starting out reloading and have been doing a bit of research on the subject before I go ahead and do the job and there's one thing that I cant get me head around.

I'm using a 30.06 cartridge for this and measured the once fired brass against a loaded factory round with a hornady headspace guage and the once fired brass is shorter than the loaded factory round. I thought the brass was supposed to stretch?

Sizes are, once fired brass 2.035.5, loaded factory round 2.038.5

Can anyone help me out?

[Tiiger]

As cartridges are fired the necks will stretch, that's right.

We must be talking different brass and/or factory ammo here? You couldn't have two of the same factory cartridges with the same length brass, fire one and had it get shorter.

About for the 'short' once-fired brass... Brass neck length isn't an absolute, there's a minimum and maximum length to be safely chambered (or chambered at all if neck is too long).

Have the cases been trimmed? Depending on brand of trimmer some trim shorter than others to allow more time between required trims.

Likewise with the factory ammo. One brand could make their necks to a slightly different length than the next.

Don't shoot it, don't know exactly what the min/max length neck is for 30-06, but someone will have it. A little variance is common though.

[Carter]

Sizes are, once fired brass 2.035.5, loaded factory round 2.038.5

Err. Think something been mismeasured there.

30-06 case length should be 2.494" give or take, not possible to be 2.0", the whole shoulder and neck would be missing.

[glenn curnow]

Im talking about the length of the brass between the heel of the head and the datum line on the shoulder , not the oal of the case.

[Carter]

Got it, assumed we were talking OAL of the brass.

How hard was it to chamber the brass? Difficult to close the bolt? Could suggest the headspace is a little short.

What rifle also?

[glenn curnow]

30.06 first time fired case, I haven't tried chambering it but it was fired from the gun so you would think that the case has formed to the chamber specs.

My problem Is that when you fire the factory round then you measure the case with a head space gauge [Hornady], the once fired brass is shorter than the factory round when measured with the head space gauge.

I cant understand how the case can end up shorter in this instance .003" I thought that the case should increase in length, not shorten?

[Khan]

I can explain

Your cartridge is obviously smaller than the chamber, has to be so it will feed in easily and smoothly and you can close the bolt without needing to put on too much force.

When the case is fired pressure is created pushing out on the brass. In low pressure cartridges the pressure is enough to expand the sides of the brass and pull the top down if you get what I mean. Like pinching 2 side of a balloon and pulling. The shoulder to base length becomes shortened while the width increases.

When you full length size the fired brass it pushes the sides in again and the top will push up again making the case taller.

Over your next few shoots measure the brass after shooting and after resizing. If you're full length sizing with the same loads you'll find the brass goes down when shooting and up after sizing.

Happens commonly in 5.56mm, low pressure loads for cast bullets etc.

It seems counter intuitive but there it is.

[Carter]

Well I learned something new.

[Jack V]

I agree with Khan that can happen.

You are making your life complicated worrying about measurements that don't mean much , just make sure your cases fit the chamber with minimum headspace.

Your gun, a sizing die and some knowledge is all you need. Just find and check the OAL of the shortest case in a batch and trim to that, lightly chamfer in and out, then if needed size to fit chamber.

I have never found that gauges do any better job than sizing by bolt closure feel. They are nice toys but they can complicate a simple task.

[Khan]

I agree with Khan that can happen.

I was bound to get one right eventually

Just gotta get one victory under the belt with the missus now. That's going to take longer...

[Korkt]

Adding to what Khan and Jack have said.

What you've described isn't a problem either. Search more and you will find people telling you you need to go to high pressure loads to avoid this, but it isn't a problem.

The factory loads will obviously be tested safe charges and when hand loading staying above the data minimum may still give low enough pressure loads to cause what you've describer, but there is no need to try and "fix" it.

It's fine.

(too low can be an issue, but that's another topic)

[glenn curnow]

Thanks Khan that's helped a lot, and to all you blokes, Glenn.

[Chronos]

I agree with Khan that can happen.

You are making your life complicated worrying about measurements that don't mean much , just make sure your cases fit the chamber with minimum headspace.

Your gun, a sizing die and some knowledge is all you need. Just find and check the OAL of the shortest case in a batch and trim to that, lightly chamfer in and out, then if needed size to fit chamber.

I have never found that gauges do any better job than sizing by bolt closure feel. They are nice toys but they can complicate a simple task.

Yeah I agree Khan nailed it but the op is doing the right thing measuring and trying to understand what's going on. This is more common in cartridges like 30-06 and 6.5x55 where factory ammo must be safe in old clunkers chambered for the round.

The number of times I've seen reloaders ask about f/l sized brass that won't chamber would amaze you. People running their die down until it sizes the case walls. It pushed the shoulder up making the case head to datum point dimension longer.

Chronos

[Jack V]

Yep and that is why I don't use traditional Full length size dies . You have to actually oversize the case first to get it right as it comes out of the die . In a body die you don't have to oversize anymore than the natural spring back ( elastic limit ) of the brass which is generally .001 to .002 and no expander ball to pull anything out of shape as the case comes out .

[Khan]

Thanks Khan that's helped a lot, and to all you blokes, Glenn.

No problem mate.

It's a weird one to figure out.