Well, yeah, but it depends on the definition. In my vocab, 'doubling' is short for 'double discharging', which only happens if both barrels actually discharge!

The fact that an intercepting sear will catch the tumbler prior to discharging the second barrel is no consolation whatsoever. The gun still cannot be fired until opened and re-cocked, so all you've really saved is one round of ammunition! If facing DG at the time, you are still just as deep in clag!

I'm afraid I can add little of value to the original discussion on doubling, because in all my years of shooting and hunting with DRs, it has never happened to me. I also have absolutely no clue how my trigger finger gets from one trigger to the other! I know it has happened because there are two bullet-holes on the buff's shoulder, or 2 dead boars, but it is controlled by a part of my brain which is flying solo. I was brought up on SxS shotguns from a young age, so I guess it's simply become instinctive.

The earlier suggestion of buying a cheap double-trigger SxS shottie and busting a box of clays a week is a very good one. When you can concentrate fully on the target, and your trigger-finger does the rest automatically, you will have eliminated 'operator error' as a cause of doubling. Target shooting with your DR at the range will not achieve this.