Headspace questions .224 Valkyrie questions and help needed.

[TheDomFather]

Folks,
If you have seen some of my threads in the past you know I am struggling to find accuracy in my new .224 valkyrie rifle. Today I took some headspace measurements. Hornady does not yet make a modified case where I can measure OAL but today I took some of my fired and unfired cases and measured them. Here are the results:

Federal Fusion 90gr factory loads unfired headspace measurements:
1. 1.255” 2. 1.256” 3. 1.255”
Federal Fusion 90gr factory loads fired case headspace measurements:
1. 1.265” 2. 1.264 “ 3. 1.265”

Should my shoulder be moving 10 thousands after firing? This seems to be excessive to me and I am wonder if the reports of some bad chamber reamers are true and my barrel was chambered incorrectly? I have a note out to the manufacturer who has sent me a return form so they can test it as well. However I am worried they are just going to fire a few federal factory 90gr SMK through it and not take headspace measurements?

I am also seeing the same delta in headspace measurements on my reloads:

New sized cases are:

1. 1.252” 2. 1.252” 3. 1.252” 4. 1.251”

Reloads after firing:
1. 1.264” 2. 1.266” 3. 1.265” 4. 1.265” 5. 1.266”

Again we are seeing at least 10 thousands of shoulder movement after firing.
Please give me your thoughts and guidance??
Thanks,
Dom

 

[243winxb]

Ease a fired case back into the chamber. Will the bolt lock closed?

Autos may open early on firing. Brass may stretch longer then the chamber. Head to datum.

 

[243winxb]

After checking the new SAAMI drawings of cartridge and chamber, your measurements are within spec.

Adjust the sizing die to only bump the shoulder back .005"

Overall , looks like a 1 1/2" rifle. https://www.americanrifleman.org/articles/2018/5/21/tested-inside-the-224-valkyrie/

 

[Blue68f100]

A set of head space gauges will check your chamber. The set I have is 0.004" difference between the two.

Don't remember if your gun is a bolt gun or simi-auto. I have just finished reaming the chamber on my barrel, set at min head space. I also made a case gauge out of the barrel drop off to use to check ammo.

I agree with 243winxb on only moving the shoulder back a bare min. I would even try 0.002-0.003" or less on a bolt gun. If this is a simi-auto it may have the same characteristics of the 6.5 CM. Meaning there is a lot of gas pressure higher than normal requiring a slightly smaller gas port or adj gas block.

 

[243winxb]

Headspace may be closer, if the bolt and barrel are from the same manufacture.

Its an auto home built parts gun.