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Headspace Help. What's Going On?

M

Magstang1

Sergeant
Full Member
Minuteman
Nov 20, 2010
124
2
41
Michigan
Rifle: Tikka Tac .233
Ammo: PMC Bronze .223
Dies: RCBS Full length .223 set

When I measure a fired case from this rifle, they are measuring in the 1.4480" area, which seemed short to me.

I started to set up the dies for this rifle, and ran out of adjustment before the die touches the shoulder. My press was camming over and the brass was growing to 1.4505" or more.

Before I did anything drastic like grinding the bottom of the die body off, I checked a few things.

I was using a RCBS Rock Chucker to set up. I moved the die over to my LNL AP to see if maybe a different press and shellplate would make a difference. Nope.

I got the rifle out and dropped the brass in. Chambers just fine, even at 1.45?"

Ok??

I measure a new PMC Bronze from the same box I was shooting. 1.4510 - 1.4530.

How is my fired brass shorter than factory ammo?

What should I set my resizing die to for length?

The only thing that I did that could possibly have an effect on length was run the fired brass through a Lee universal decapping die to knock the primers out, but that doesn't touch the shoulder.

Help?!

A little more info to add to the confusion:

Various ammo I have laying around

Factory Lake City 5.56: 1.4510
My reloads for an AR: 1.4560

All of this ammo chambers fine in the gun. How can my fired brass be so much shorter?
 
Re: Headspace Help. What's Going On?

You press isn't camming over before the die touches the shell holder. Camming over happens when the die is screwed in until it touches the shell holder then a little bit more. The expander ball is catching and actually pulling the shoulder forward.
Heres what I do:
Screw the sizer die until it touches the shell holder.
Don't tighten the lock ring yet and lower the ram.
Place two washers on top of the shell holder and raise the ram.
Press down on the press handle so the press cams over center.
Tighten the lock ring.
Remove the washers and begin sizing.
Check set-back and adjust as if you were setting it up the first time.
The washers on top of the shell holder removes the slop built into the threads and it is the best way I've found to get consistent set-back.
Don't forget to lube the inside of every third-fifth case neck o the expander ball doesn't drag.
Hope this helps.
 
Re: Headspace Help. What's Going On?

The die was touching the shell holder.

The expander plug was removed from the die.

I tried it on both presses with different shell holders.

I guess a clearer explanation would be that the die is screwed in all the way to the shell plate and not bumping the shoulder.

But, do I need the shoulder that far back? Loaded ammo that is longer chambers fine. How did it get that short?
 
Re: Headspace Help. What's Going On?

Magstang,

You do not mention what you are measuring your headspace with. I would suggest buying a Headspace gauge and case gauge. Me personally I do not like to guess with my reloading. I bought a Hornady headspace gauge and bump back the shoulders. Sinclair has an article on their site. This is not hard and fast but will provide some concepts you can expand on.

Setting Up sizing die
 
Re: Headspace Help. What's Going On?

Is this the first time you used this sizer die or have you used it to size other brass.
Sorry for so much in the question but when I originally typed...is this the first time you used a sizer...sounded like a smart ass
 
Re: Headspace Help. What's Going On?

This is a new set of dies that I just bought.

I have not used them before. I bought another set so I wouldn't have to mess with the dies set up for my AR.
 
Re: Headspace Help. What's Going On?

Have you tried to size brass that was fired through another rifle through the new die?
If you have/do and they don't size I would give RCBS a call. They will surely make it right.
 
Re: Headspace Help. What's Going On?

I guess my question really is; how is my brass shorter after firing?

I understand why the die is not bumping the shoulder back. In fact, the brass is growing from the resizing. The shoulder of the die is still quite a way off from the shoulder of the brass. If I was certain that the shoulder actually needed to be set where I measured it at, I would just mill the base of the die body down.

If I can chamber brass with a considerably longer headspace, then I don't see the need to resize my brass and set the shoulder that far back.

The question is; how did it get there?

Thanks for the replies so far!
 
Re: Headspace Help. What's Going On?

I still have not figured out how your brass appears to be shortning it's headspace after firing. rechecking your numbers is quite baffling. I have never seen the shoulders actually set back after firing. You may want to place a call to the rifle manufacturer as well. There may be a problem with your rifle's chamber.
 
Re: Headspace Help. What's Going On?

My rifle's manufacturer is in Finland.

It's imported by Beretta, who I hear is terrible to deal with.

I bought it used so I doubt there is any warranty anyway.

It's confusing to me as well. I checked a number of cases. The only thing that even has a chance of affecting this is my universal decapping die. I highly doubt that though. I took the decapper out and dropped a piece of brass in it. There is no restriction at all, and it's not bottoming out.

I guess I'll grab a couple more different kinds of factory ammo and shoot it again.

It just doesn't make sense. If the chamber really was that short, I shouldn't be able to chamber longer rounds.
 
Re: Headspace Help. What's Going On?

How long since you changed the battery in your caliper?
 
Re: Headspace Help. What's Going On?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Magstang1</div><div class="ubbcode-body">I guess my question really is; how is my brass shorter after firing?

I understand why the die is not bumping the shoulder back. In fact, the brass is growing from the resizing. The shoulder of the die is still quite a way off from the shoulder of the brass. If I was certain that the shoulder actually needed to be set where I measured it at, I would just mill the base of the die body down.
If I can chamber brass with a considerably longer headspace, then I don't see the need to resize my brass and set the shoulder that far back.

The question is; how did it get there?

Thanks for the replies so far!</div></div>

your factory chamber is larger than new brass.when you shoot new brass.... the sides blow out/expand to touch the chamber walls....thus pulling back the neck...
bill larson

 
Re: Headspace Help. What's Going On?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: insight3b</div><div class="ubbcode-body">How long since you changed the battery in your caliper? </div></div>

I'm measuring new ammo side by side with the fired brass at the same time. I only made it half way through the last box last time out.

I really don't see the battery affecting the measurements when they are repeatable.

But to answer your question; I don't know when the last time I changed the battery was.
 
Re: Headspace Help. What's Going On?

I use a Hornady headspace gauge with the proper .330" insert for the .223 Remington.

I use a digital caliper and I zero the caliper after attaching the gauge and body on the jaws. My numbers are as follows:
New unfired brass- 1.456"-58"
Fired brass in my autoloaders: 1.463"-64"
Re-Sized brass- 1.458"-59"

When I drop the 1.458"-59" resized brass into a Wilson type headspace gauge, it registers nearly to the minimum headspace in the gauge. The resized brass chambers perfectly in the autoloaders and in my 700 V in .223 Rem.

Are you using the .330" bushing?

I don't know why your measurements are so different.

I have a regular RCBS 223 Rem. die and a RCBS Small Base die in .223 Rem. and they both push the shoulder back to 1.458"-59" with no problem.
 
Re: Headspace Help. What's Going On?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: FLIGHT762</div><div class="ubbcode-body">I use a Hornady headspace gauge with the proper .330" insert for the .223 Remington.

I use a digital caliper and I zero the caliper after attaching the gauge and body on the jaws. My numbers are as follows:
New unfired brass- 1.456"-58"
Fired brass in my autoloaders: 1.463"-64"
Re-Sized brass- 1.458"-59"

When I drop the 1.458"-59" resized brass into a Wilson type headspace gauge, it registers nearly to the minimum headspace in the gauge. The resized brass chambers perfectly in the autoloaders and in my 700 V in .223 Rem.

Are you using the .330" bushing?

I don't know why your measurements are so different.

I have a regular RCBS 223 Rem. die and a RCBS Small Base die in .223 Rem. and they both push the shoulder back to 1.458"-59" with no problem.

</div></div>

Yes, I'm using the .330 insert and zeroing after the gauge is set up.

Your numbers are right in line with the numbers I'm getting for my AR. I'm using RCBS small base dies for that as well.

The problem arises when the fired brass measures shorter than factory ammo, and shorter than my other reloads.

Bill Larson: Your explanation of the brass shrinking in length due to expanding in diameter seems plausible, but wouldn't the pressure inside the case be evenly distributed, or even focused on the bottle kneck of the brass, preventing shrink?

I'll admit that I'm a newish reloader, but this is beyond me.
 
Re: Headspace Help. What's Going On?

That's a good question. I have no idea. I was told the rifle was stock from the factory.
 
Re: Headspace Help. What's Going On?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: FLIGHT762</div><div class="ubbcode-body">Was it re-chambered at some point to .223 Ackley Improved?

http://www.6mmbr.com/223rem.html </div></div>

you would be able to tell by looking at the shoulder angle. how does it compare to another case?
 
Re: Headspace Help. What's Going On?

If it won't properly size brass from another rifle I would give RCBS a call. I'm stumped otherwise
 
Re: Headspace Help. What's Going On?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 1236</div><div class="ubbcode-body">Make a chamber casting </div></div>

I've never heard of this. How do I do this?
 
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