Headspace gauge vs fired brass measurements

[Just Say Moe]

Regarding these measurements with my Hornady comparators:
6BR Remage setup/ R700 action
My question is the 0.029" difference between the Go gauge and fired brass - Should I just Full Length bump to 1.087 and disregard the Go gauge measurement? Why the big difference? There are no signs of case head separation.

My 20 Vartarg has only 0.009" difference.

Forster Go gauge	1.160
Go gauge 2 layer tape (bolt will not close)	1.162
New Norma brass	1.155
5 fired case avg Norma	1.189

 

[Doug Beach]

Will your bolt close on a no go, or taped go? I bet it will...

 

[K22]

I don't base any die sizing settings / adjustments based on the case head space of new unfired cases. First I full size all new cases with zero shoulder set back just to uniform the cases and ensure the neck is in alignment with the body of the case and to set uniform neck sizing. The die is set to just touch the shoulder to prevent lengthening the case by extrusion in the die.

Once the cases are "fire formed" to the rifle's chamber I take case head space measurements on a few cases (primer removed). I then set the full sizing die to set the shoulder back .001 to .002" from the fired case measurements leaning more towards the .001" value. I double check in the rifle chamber to make sure that I have enough sizing without having to force the bolt close. The goal here is to size only enough so the bolt closes with only slight resistance thus avoiding over sizing the cases.

With new cases sometimes it might take a few additional "fire forming" shots to obtain a consistent die setting to achieve the consistent desired (.001 to .002") shoulder set back.

I'm not sure that I'm interpreting your above data correctly but 1.155 new to 1.189 expansion after firing seems like an awful lot to me. Are you sure that's correct?Also I'm not sure what you mean by a "go gauge" relative to case sizing issues.

 

[Just Say Moe]

Will your bolt close on a no go, or taped go? I bet it will...

No, it will not close. That adds to my confusion.

 

[Just Say Moe]

I'm not sure that I'm interpreting your above data correctly but 1.155 new to 1.189 expansion after firing seems like an awful lot to me. Are you sure that's correct?Also I'm not sure what you mean by a "go gauge" relative to case sizing issues.

Thanks K,
That much difference was my concern. I measured 26 fired cases (with primers) and most were 1.189 and 1.190. They averaged 1.189. I will remove the primers and remeasure tomorrow.

 

[Uncle Ed]

The Hornady type comparator must have the primer removed to get accurate measurements. A fired primer might be deformed or back out of the primer pocket and cause longer false case readings.

 

[Rick300]

Thought I would jump in here as I was going to start a new thread along the same lines.
I will be putting on a 20 Vartarg Remage barrel soon and a go gauge is 6-8 weeks out. I bought some Vartarg brass from Sleeping Giant brass and was thinking maybe I could use the brass for a go/no go gauge?
What would be the issues with that?

 

[klamathsteel]

The Hornady type comparator must have the primer removed to get accurate measurements. A fired primer might be deformed or back out of the primer pocket and cause longer false case readings.

What Uncle Ed said. ^^^^^^ I have an old RCBS JR press with a universal decapping die in it. It is the very first stage of my reloading process.

 

[243winxb]

Full Length bump to 1.087" Does brass chamber & allow the bolt to close? Yes/Done. No/Bump shoulder till brass fit chamber.

 

[338 dude]

Thought I would jump in here as I was going to start a new thread along the same lines.
I will be putting on a 20 Vartarg Remage barrel soon and a go gauge is 6-8 weeks out. I bought some Vartarg brass from Sleeping Giant brass and was thinking maybe I could use the brass for a go/no go gauge?
What would be the issues with that?

New brass is usually very short of course you could always move it out when you get your gauge but you will likely have to rework any load data that you’ve acquired

 

[slobhunter2]

Any chance your barrel is actually a 6 Bra chamber, can you post a pic of fired and un fired brass side by side?

 

[Just Say Moe]

Any chance your barrel is actually a 6 Bra chamber, can you post a pic of fired and un fired brass side by side?

Firmly reseating the primers made no difference in the measurements
decapping the primers made no difference in the measurements

Here is a pic - Norma brass if that makes a difference
measurements
fired/new
Neck 0.270/0.264
Shoulder 0.460/0.455
approx middle 0.466/0.458
base ahead of groove 0.469/0.466

 

[Just Say Moe]

Full Length bump to 1.087" Does brass chamber & allow the bolt to close? Yes/Done. No/Bump shoulder till brass fit chamber.

FL sized fired cases 1.187 and 1.188 chamber and bolt closed. Looks like I will go this route!

 

[243winxb]

https://forum.accurateshooter.com/threads/6br-measurement-to-datum-line.3568169/

5 fired case avg Norma

1.189"

Correction on sizing? Should bump back to 1.187" Looks to long?

But first the rifles headspace needs to be set correctly?

Something is not right?

 

[Dusty Stevens]

Size them but do not bump the shoulder if the bolt closes

 

[searcher]

Should I just Full Length bump to 1.087

You say your fired brass all measures 1.189. I'd bump .002" or so to get you to 1.187. If your shoulders were fully blown forward - this is where I'd bump to.

 

[Just Say Moe]

You say your fired brass all measures 1.189. I'd bump .002" or so to get you to 1.187. If your shoulders were fully blown forward - this is where I'd bump to.

Sorry typo - yes 1.187!