6 dasher brass - fireform length??

[operator1]

Just built a 6 dasher and am trying to get my brass fireformed. I am using the false shoulder method with 30.5 gr Varget, 107 smk and cci 450 primer. I am using Lapua blue box brass and am getting 1.538 after fireforming. Chamber is 1.555. Is this too short? Any advice on how to get better results?
Hotter load?

 

[waverly]

1.538 is fine

I just measured two different sets of Dasher brass. One a 1k light gun, and the other is a nine twist hunting rifle. They both measure the same as yours. Good square shoulders are important, but at that length you may never have to trim it.

I'd say your load is fine. Shoulders are nice and square. I also shoot Varget, but use BR-4 primers, and Berger 105's in the orange box ( old vld's)

Being a little shorter than the 1.555, just make sure you keep the throat clean and carbon free. I use the cream of wheat method the first firing.The second firing I use a reduced load of Varget(around the same charge as you). Third firing is a full load. It works for me.

I don't have a cure to get longer brass when fireforming. I use the same false shoulder method, and just make sure I get a nice snug fit when closing the bolt.

Good luck, and just go have some fun with it. Dashers just plain shoot.
Waverly