Hoping you can solve this enigma. My typical case runout for fired Lapua neck turned brass is 0.001 or better. Prior to the latest firing, I annealed the brass and shot it it. After firing it (before resizing it) I was surprised to see runout around 0.002-0.0025. Resizing it kept it about the same. Nothing else has changed (same rifle, etc.). This brass is on it's 8th firing. Could my annealing have caused this? This was my first time annealing this brass. Or, as the brass ages, does runout increase? Any ideas?
- Thread starter hkfan45
- Start date
Annealing was done on a Bench Source.
Not familiar with that particular model, but if it's like the other ones I have seen the cases ride against a surface causing them to spin? If so, maybe you annealed too much?
Is it all 5 cases that run out like this? Brass shouldn't really "wear" as such, though 8 firings is kind of a lot to go without annealing, from what I've seen and understand
Is it all 5 cases that run out like this? Brass shouldn't really "wear" as such, though 8 firings is kind of a lot to go without annealing, from what I've seen and understand
What type of die did you use when you resized? After you fire brass a few times, the necks can thicken up because of case growth. Check the thickness of your necks and see if has changed since you first turned them. If so you might need to turn them again.
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Annealing softens work-hardened brass. Sizing should bring the cases fairly close to true with minimal runout.
Fired cases with runout might indicate your chamber is slightly off-true with bore line.
Annealing after every shooting may help keep all your brass consistent.
Fired cases with runout might indicate your chamber is slightly off-true with bore line.
Annealing after every shooting may help keep all your brass consistent.
What's odd is that this same brass fired in this same chamber always gives runout of 0.001 or less (most 0.0005). After annealing and firing, the runout is now 0.002-0.0025 with this brass.
When you annealed the brass you made it softer so one of two things occured. 1. Like the fella above said, your chamber is off a little 2. The side to side wall thickness of cases vary, when you fire the case these varying thickness's move to the neck (that's why you have to trim) and after a few firings one side of the neck is thicker than the other giving you runnout. Cases grow at a much higher rate when annealing b/c of the softer brass, especially in cases with a less steep shoulder angle.
