Fired brass same size as unfired

[NJRaised]

Sorry if this question has been asked, I did search prior…

I measured my brass with mitutoyo and Hornady headspace gauge. I have been shooting FGGM 223. Prior to firing it measures 1.460”, after firing it is 1.460”, and my new starline brass is 1.460” +\- .005”

Am I blessed with an extremely tight chamber that I barely need to shoulder bump? Is this normal?

It is a chambered barrel not a prefit. Never had an issue chambering factory FGGM 223, but hornady match has occasionally not wanted to chamber without some resistance.

 

[simonp]

I think there must be an error somewhere in your measurements or method of measuring. Any brass will expand upon firing & there will be a change from unfired to fired brass. I’ve never encountered a situation like yours.

 

[acourvil]

Measure the volume, i.e., weigh the amount of water fired/unfired will hold. I think you will find that the fired will hold more.

 

[Dolomite]

Could be short chambered if you’re just measuring shoulder bump or head space. Short chambering maybe .001 over the virgin brass as to not over work the brass especially at the base. Measure the base and the SBJ to see if it’s the same. Should’ve grown at least .001 - .002.

 

[NJRaised]

My guess is short chambered. I’ve measured 10-15 pieces of fired and unfired, and they’re virtually identical. All measurements done with mitutoyo calipers and hornady headspace gauge.

I did have some issues with hornady match not wanting to chamber (without a little muscle on bolt close), so I guess it could just be a short chamber. Which my guess is,… is not a bad thing.

 

[Marine52]

Is this a bolt gun?

 

[NJRaised]

Is this a bolt gun?

Yes it is.

 

[Marine52]

Yes it is.

You need to find your rifle headspace or else you will be chasing random shoulder bumps. Get a Go Gauge for the 223 rem. I use a go gauge and then use aluminum foil on end with a smidge of paste to find exact headspace (reg foil is about .0004 - .0006” and heavy foil is right at .0008”). I do this on a newly chambered barrel and then I have a set target number for the rest of its life. If I want .002 bump, all I do is index off of the go gauge. I will confirm case fit in chamber for early sizing.

 

[bax]

Sorry if this question has been asked, I did search prior…

I measured my brass with mitutoyo and Hornady headspace gauge. I have been shooting FGGM 223. Prior to firing it measures 1.460”, after firing it is 1.460”, and my new starline brass is 1.460” +\- .005”

Am I blessed with an extremely tight chamber that I barely need to shoulder bump? Is this normal?

It is a chambered barrel not a prefit. Never had an issue chambering factory FGGM 223, but hornady match has occasionally not wanted to chamber without some resistance.

According to SAAMI, headspace at the .330 mark is 1.4666 minus 7 thou. You could have a chamber that is 1.460, just on the short end of SAAMI. You still need to bump a little to insure that you can chamber a dirty round. The amount of bump is up to you but 2 thou is the common number. The post-bump dimension depends on the size of your chamber and not on some SAAMI spec. For example, if your chamber was 1.470 then (assuming a 2 thou bump) post-bump your brass should measure 1.468; if your fired length as 1.455 then your post-bump dimension would be 1.453.

 

[Marine52]

According to SAAMI, headspace at the .330 mark is 1.4666 minus 7 thou. You could have a chamber that is 1.460, just on the short end of SAAMI…

The 1.4666 - .0070 shown by SAAMI is not the headspace. These are the SAAMI cartridge dimensions. The SAAMI rifle headspace specs for a 223 rem are 1.4636 (min) to 1.4736. (max). A Go Gauge should be at SAAMI min.

Get a Go Gauge from a good company like Manson. If your rifle bolt will not close on the go gauge then it is out of spec.

 

[MO Fugga]

I think there must be an error somewhere in your measurements or method of measuring. Any brass will expand upon firing & there will be a change from unfired to fired brass. I’ve never encountered a situation like yours.

I have some .458 SOCOM brass with 20+ firings, never been trimmed or annealed. Shit just keeps on truckin'.

 

[Doom]

Your measurement is after the brass expanded to fill the chamber under pressure. It has undergone what is typically described as springback. The data dimension of the chamber exceed what your comparator measured. I would say your chamber is close to minimum.

 

[bax]

The 1.4666 - .0070 shown by SAAMI is not the headspace. These are the SAAMI cartridge dimensions. The SAAMI rifle headspace specs for a 223 rem are 1.4636 (min) to 1.4736. (max). A Go Gauge should be at SAAMI min.

Get a Go Gauge from a good company like Manson. If your rifle bolt will not close on the go gauge then it is out of spec.

Right you are, my mistake.

I use Forster headspace gauges and mitutoyo caliper that measures to .0005 precision. I made some measurements:

Try to measure my .308 headspace gauge using hornady .400 comparator body. Gauge is forster marked 1.630. Measurement says that my headspace gauge length is 1.625. In order to know the actual base-to-datum case length, I need to add .005 to the measurement.

Repeat for my .223 headspace gauge using hornady .330 comparator body. Gauge is forster marked 1.4636. Measurement says that my headspace gauge length is 1.461. In order to know the actual base-to-datum case length, I need to add .0025 to the measurement.

Repeat for my 300 PRC headspace gauge using hornady .420 comparator body. Gauge is JGS marked 2.2000. JGS made my reamer and the gauge. Measurement says that my headspace gauge length is 2.1965. In order to know the actual base-to-datum case length, I need to add .0035 to the measurement.

I believe that the difference between stated headspace gauge length and the measured length arises because the comparator bodies are not exactly the right dimensions. At the moment, I trust the headspace gauge markings.

My .308 chamber was cut using my JGS reamer and the forster headspace gauge plus one piece of thin scotch tape. My 300 PRC chamber was cut using my JGS reamer and headspace gauge plus one piece of thin scotch tape. I think that those calibrated measurements match my chambers. I will verify when I have some recently fired brass.

Notice that in each case, my measurements were between 2.5 and 5 thou less than the actual gauge length. You were measuring 1.460. If your .223 comparator body is like mine, you need to add .005 to the measurement for fired case length in order to get the actual case dimension. That would give you 1.465 - a bit short but .0014 longer than the minimum spec.

I agree with Marine52, buy a quality GO gauge and check your chamber.