Not as stressful as combat situations, but I'm so used to my Red Label shotguns that I use for partridge, that when I swap to my Benelli for ducks and geese I have problems. I always try to find the safety on the tang rather than the cross-bolt, and sometimes I've only taken two shots and gave up, forgetting I had another one available with the semi-auto. Not only embarrassing, but potentially dangerous.
Yeah, I think that being familiar with the weapon makes a big difference, especially if you have one type that most operations are done by reflex.
Quando omni flunkus moritati