Hey, Hey! 1/2" groups in my doubles would be great!

I'll take some time and measure as you describe and see what I get. I also only use new brass for hunting.

I'm sure that double 12ga with slugs is impressive as well.

Cheers,

Todd

That looks like a brittle, bad piece of brass; throw it away and forget about it. Your chamber is fine as the brass in the picture shows no bulging. Excessive headspace does not cause longitudinal fractures; they are characterized by radial ones, and for several reasons, are really, really, rare.