The actual shootout didn't actually occur at the OK Corral itself, but in a vacant lot 90 or so feet from the OK Corral, with 30-35 shots being fired in 30 seconds.
Wyatt Earp most likely used a Smith & Wesson Revolver, either a Model 3 or a Schofield at the OK Corral just like Virgil Earp, Also Wyatt and Virgil were not wearing holsters at the OK Corral.