One of the fellow students in my concealed carry live fire qualification was shooting .38 Special with a 4" S&W revolver double-action (don't know what model) and his groups were smaller than most of those who were shooting striker-fired snubbies. Course was 10-shot each at 3, 5, and 7-yards, and he wasn't taking his time pulling the trigger nor emptying the spent cases and re-loading with a speed loader. He wasn't a Miculek (sp), -- that's not the point -- just an average Joe who spent the time to learn how to use his revolver. I was impressed.
Right or wrong, my revolver shooting is done single-action. For the live fire qualification, I used the Glock 27 and the Randall 1911.