Brass shoulder measurements. Different brass mfg

[Dimner]

I have two sets of brass in 30-06. PPU and Starline. These are for two sporter hunting rifles, but they are both very accurate. I use PPU in my Tikka and Starline in the custom mauser.

I know shoulder measurements are relative, so these are the relative measurements.

Tikka fully fire formed shoulder 2.0445
Tikka shoulder bump back to 2.0420

Custom mauser fire formed shoulder 2.0465
Custom mauser bump back to 2.0440

Using my forster bench rest full length sizing die, I have verified my preferred bump amount for each rifle by the bolt close method.
The FL resizing is being done after annealing, with the same lube process, same shell holder, and the FL die at the exact same setting.

My question is.....

My expectation was that regardless of head stamp I would end up with the same shoulder measurements, since I'm using the exact same die settings . Then I realized the brass alloys are probably a bit different and thus the hardness different between headstamps. Is this the reason for the different shoulder measurements?

Second question... Was it just a lucky coincidence that I am getting a 0.0025 bump on both head stamps?

 

[GLShooter]

Yes and yes

 

[Walt Krafft]

Fully fire formed shows the headspace dimension on the two rifles is 0.002 different. That could easily be in spec. Try swapping brass between the two rifles to see if the numbers change.

 

[Straightshooter1]

I have two sets of brass in 30-06. PPU and Starline. These are for two sporter hunting rifles, but they are both very accurate. I use PPU in my Tikka and Starline in the custom mauser.

I know shoulder measurements are relative, so these are the relative measurements.

Tikka fully fire formed shoulder 2.0445
Tikka shoulder bump back to 2.0420

Custom mauser fire formed shoulder 2.0465
Custom mauser bump back to 2.0440

Using my forster bench rest full length sizing die, I have verified my preferred bump amount for each rifle by the bolt close method.
The FL resizing is being done after annealing, with the same lube process, same shell holder, and the FL die at the exact same setting.

My question is.....

My expectation was that regardless of head stamp I would end up with the same shoulder measurements, since I'm using the exact same die settings . Then I realized the brass alloys are probably a bit different and thus the hardness different between headstamps. Is this the reason for the different shoulder measurements?

Second question... Was it just a lucky coincidence that I am getting a 0.0025 bump on both head stamps?

That the Mauser has an apparent .002 difference in headspace, the .002 in bump doesn't really surprise me, even though you're using the same die. Not only could it be the difference in alloy hardness, but the difference in case wall thickness can be a key factor too.