Question about Case Headspace Measurement

[INTJ]

Do not pass GO and do not collect $200.00

What type/make .223 rifle do you have and does it have a barrel nut.

He does indeed get to pass go and collect $200.

The last two LR BR barrels I chambered came out a tad tighter than I meant. The bolt won't completely close on a go gauge. However, brass chambers just fine and as long as the bolt will close on the brass I am fine. I just bump the shoulder .002 to .003" each firing and I have no issues.

I will say there are potential issues with a tight chamber. It may take a custom die to size the brass enough, and if you want the ability to shoot various kinds of brass and ammo, a tight chamber my prevent that.

The best practice is to make sure the bolt closes on a go gauge, but in many applications it isn't a big deal if it doesn't.

 

[INTJ]

I know what it is I just haven’t heard that term so it caught my eye.
Hell I even wrote it down

Radial expansion is a correct term. Of course, you can shoes to say "gets larger in diameter" instead.........

 

[dellet]

Sounds like a low pressure load.

A couple thoughts. As other have said, diameter expansion happens first and will shorten the length, before stretching the length. This is very common with subsonic loads.

Your thinking is correct, but is poorly applied. There is no way to know for sure if your fired case is longer or shorter than before it was fired. It might be possible to measure all of your unfired cases and find a few shorter than your fired case. A sample of one each is not enough to make any real data points.

Measure and mark a few cases before and after firing, “compare” those measurements. It’s not a precision instrument as you found out, always zero your caliper will help. Just remember it’s called “comparator” for a reason.

 

[ronsatspokane]

Do not pass GO and do not collect $200.00

What type/make .223 rifle do you have and does it have a barrel nut.

No barrel nut. It's an older CZ 527 FS. Go gauge is PTG. The construction of the barrel (the way the sight is mounted) would make it very difficult to adjust headspace unless one could find a reamer that matches the chamber very closely and then just touch it a tad to bump the shoulder a thou or two. I'm not going to touch it though. Thing thing feeds fine and no bolt close issues plus it shoots 1/2 moa with the 50 grain vmax lit off by CFE223. Just a short chamber is all and not by much.

My point in this was that it could be a reason the OP is seeing less headspace on fired rounds.

 

[Ned Ludd]

I purchased a couple of those Hornady "anvils" thinking they would provide a flat and steady base on which to take measurements. They did not. Far from it. Measurements taken with those were all over the map. I immediately went back to using the comparator/insert on side, and the naked caliper jaw on the other. In my hands, that provides a much more steady and consistent measurement than the anvil. Before you go down the rabbit hole of trying to figure out how a fired round could end up shorter than virgin brass, try taking multiple measurements using your comparator both with/without the anvil and determine whether the anvil itself may be causing a measurement discrepancy.

 

[South Pender]

All good suggestions, guys, thanks. I'll try the measurements without the "anvil."

 

[rjtfroggy]

I purchased a couple of those Hornady "anvils" thinking they would provide a flat and steady base on which to take measurements. They did not. Far from it. Measurements taken with those were all over the map. I immediately went back to using the comparator/insert on side, and the naked caliper jaw on the other. In my hands, that provides a much more steady and consistent measurement than the anvil. Before you go down the rabbit hole of trying to figure out how a fired round could end up shorter than virgin brass, try taking multiple measurements using your comparator both with/without the anvil and determine whether the anvil itself may be the cause.

I have found the same thing and now do it like this.
Someone should design a shell holder for calipers so everything is level and measurements come out the same.

 

[K22]

@K22
Dude’
Radial Expansion ? Never heard that

A quote from the Rifleman's Journal: "brass fired at normal pressures springs back in both length and diameter, both need to be addressed in resizing in order to make the brass hold bullet again and go into the chamber properly. Brass that is only neck sized will hold the bullet, but will chamber hard and with each firing will chamber harder yet. The reason for this is that it essentially has no headspace, just little spring back and the radial dimensions also have insufficient clearance."

I'm not expert but my experience with neck sizing reflects German Salazar's above statement published in the subject journal. He goes on to explain that full length sizing addresses both the length and radial expansion of the case.

PS: I'm not a "dude".

 

[JFrank]

A quote from the Rifleman's Journal: "brass fired at normal pressures springs back in both length and diameter, both need to be addressed in resizing in order to make the brass hold bullet again and go into the chamber properly. Brass that is only neck sized will hold the bullet, but will chamber hard and with each firing will chamber harder yet. The reason for this is that it essentially has no headspace, just little spring back and the radial dimensions also have insufficient clearance."

I'm not expert but my experience with neck sizing reflects German Salazar's above statement published in the subject journal. He goes on to explain that full length sizing addresses both the length and radial expansion of the case.

PS: I'm not a "dude".

please forgive me for the assumption.
J