John: The age and wear is an after the fact issue. When those older British doubles were new, they were designed to be shot as I stated. When age and wear are factored in, all bets are off. I've probably only shot a total of five or six Brit doubles, but always right barrel first. At any rate, my point was not from a regulation issue, but the persistent malady Merkel doubles are afflicted with, that of doubling. My new (relatively) VC in 450 I've pulled the rear trigger first on a few occasions, but I cant remember if the barrels shot to POI, but the important point (and to the OP's query) is it did not double and ANY double, old, new, doesn't matter that doubles when only ONE (or either) trigger is pulled, has a SERIOUS issue. J

A good principle to guide me through life: “This is all I have come to expect, standard lackluster performance. Trust nothing, believe no one and realize it will only get worse…”