Targetmaster in garland will do bird and buck only (lead only, no steel), any type shotty, no slugs. The outdoor garland range on pleasant valley will do slugs but must have stock and rear sights.
If you want to have some fun with that shotgun you should attend one of the Tactical Shotgun Matches at the Dallas Pistol Club. There is one this Sunday.
I was at the Garland public range today and I want to clarify this quote. The slugs/rear-sight requirement only applies to their rifle range. They also have an area on the end of their pistol range where you can shoot any old soft lead shot at short range with whatever sights you want. They give you cardboard boxes to shoot at (probably to keep your aim low). I reduced a box to dust with 50 rounds of 00 buck and now I've got an awesome bruise growing on my shoulder