Daryl asked what you might bring to a modern day organized live bird shoot if you were to be invited and so inclined. Of course you could field any shotgun capable of the required two shots per bird, and use anything from low pressure/low velocity loads to the more effective "high brass" 1-1/4 ouncers at 1330 speed - assuming your gun could handle a steady diet of the latter and you were comfortable with old dry wood etc without checking the gun after every two shot string for cracks or chunks split out of its head. One additional consideration at modern organized box bird races at least in one legal state is that the minimum rise (shooting pad) is at 30 yards and it goes back to 35 yards. Compare that with the 1901 Live Bird GAH where the handicap rise started at 25 and went to 33. For example Ansley Fox was shooting his Winchester 1897 at 30 yards rise and the other 23 way straights were at varying distances within that range. Griffith was at 28 with his Parker.
Letsee, you're gonna pay maybe 9-10 bucks per bird and probably drop about $350-400. for the day, assuming you don't get heavy into incremental races or the side betting. Then there's the cost of travel, lodging, etc. Dance with the gal you brung and have at it.
Oops I forgot to include the cost of practice birds.