20x47 lapua pressure signs

[PAshooter20BR]

Guys,
Here is what I have going on, I am shooting my first 100 brass I have made for my 20. I am experiencing a ejector button circle and a brass smear near it. This was at 40 grains of H4350 with a 55 grain Berger. I have backed the powder charge down two grains and still experience the same thing, it may be a little less. I would have thought it would have went away by decreasing powder charge but it didn't. Gun shoots lights out with the 40 grains and I have not experienced any heavy bolt lift. Firing pin is bushed. Any thoughts would be great.
Thanks
Brandon

 

[xswanted]

I'm assuming lapua brass.

I had a 20BR that would have ejector marks no matter what I did powder wise.

If your primers aren't popping and you're experiencing a non sticky bolt I'd say you're probably okay.

Measure case head expansion on a fired round compared to a new piece of brass to be sure.

 

[PAshooter20BR]

Thank you for reply, how do I measure case head expansion?
Thanks
Brandon

 

[xswanted]

Thank you for reply, how do I measure case head expansion?
Thanks
Brandon

You need a micrometer that measures out to .00001 or at least .0001

Measure the case head. The case head resides where the "belt" would be on a magnum case.

Measure a new piece of brass and measure a fired piec of brass.

If I see more than .00025 expansion I usually back off the charge. Typically you'll see extractor marks just after this amount of expansion.

However my experience with 20cal carteidges on lapua brass is you seem to get ejector marks no matter what. I'm not sure why, but with a 20BR and a 20-250 the ejector marks were present on both cases even with light loads.