I have been shooting Trap for years. From experience if you shoot only Trap get a Trap gun. I wasted alot of money on the wrong guns for the game. Myself I use the Remington 870ct 30" barrel. Ideally an O/U is best then a semi auto second. Semi's need to be kept very clean or they jam on you at the wrong time.
Beretta 682's are nice, Browning Xt's are cheaper and they shoot very too. Beretta 391 or Remington 1100 bothe fine guns many poeple shoot the in my area.
Gun fit is a big deal n Trap. Adjustable combs and lenght of pull recoil pad adjustments really will help you score. I have shot sporting clays, skeet and 5-stand with my Trap gun I come from a famly of Trapshooters and work at a couples clubs loading targets before the automatic traps came out.
Hopefully my obeservations will aid you in some way.
Ken