Why did you go with side extraction given a 12 o'clock ignition?
I'm not sure what the jury has said, if anything about top ignition, but it does interest me.
I too have the unobtainium hammer (short fall - ~1/8") and it is double sprung.
The theory behind the negative headspace is to put pressure on the rim's perimeter to supposedly ensure more even ignition of the priming compound. The single-side extraction is an outgrowth of that, to ensure that more of the rim's perimeter is put under pressure.
The top-ignition feature is merely a copy of the proven Martini Cadet design, shown to be almost uncannily accurate in the splendid little BSA rifles.
Regards, Joe
