Interesting thread. The relationship with the gun is complex. Weight, balance and handling are subtle but affect the way we move and behave. Confidence and familiarity are factors in how we interact with the gun and the environment.
I don't believe in "lucky" or "unlucky" guns, but I do believe that certain guns suit their owners better than others. The "fit" of the gun affects not just shooting, it affects how you move and mingle with your surroundings.
I have a shotgun which consistently brings home more sharptail grouse than any other gun I use. Is it a lucky gun? Other guns fit me as well, and many of them will throw a better pattern, but none bring home the sharptail like the "old girl" does.
I doubt that this is due to some supernatural force inherent in the gun. Instead, I think that the gun simply suits my stride in the hills and dales of sharptail country - it carries well for me. My confidence in it (gained over 15 years) allows me to shoot it well. Is that luck? Finding a gun that allows me to hunt well could be considered lucky, I suppose.
Sharptail