"On another vein, what causes a Double to lose it's correct regulation?"
Some of the ones I can think of:-
- LiftingQuarter Rib - Rust between the barrels / under the rib - Lifting Rib / Rib becoming unsoldered - Very worn barrels / Loss of rifling - big change in velocity and therefore barrel time which affects regulation - Bulged barrels - Bulged chambers - Damaged crowns - Incorrect head space - causing split cases / mis fires which cause change in pressure which affects regulation