When I said "tubes" ...I was not referring to "choke tubes"...../ tubes are full length inserts that convert a barrel from a 12ga to a 20ga / or a 12ga to a 28ga / or a 12ga to a .410. ...so you have one trigger group & all 4 gages then feel and swing the same...same length, same weight.....because as skeet shooters most of us compete in all 4 gagues ( 4 separate events )....
Nothing wrong with choke tubes ....but they're different....
Before you just buy an O/U ....you need to understand what stock dimensions you need for "fit" ....so the gun hits where you look. As an example i'm a big browning fan ...but 90% of the citori models will not fit me ( drop at comb is too low, drop at heel is too low, weight is not right, length of pull is not right, throat or grip area is too thin....) ....all that little stuff is a big deal for competition target shooters....so for me, in all 4 gagues I need a parallel adjustable comb gun, 30" barrels at around 8.5 lbs....28" and 8 lbs feels whippy to me so I slap at targets instead of making a smooth follow thru.....32" barrels and 9 or 10 lbs feels like a clumsy sewer pipe on a skeet or sporting clays field ( but it's perfect for Trap)..... and if I wanted stand alone guns for each gague ( instead of full length tube sets)...I'd make sure they were made on same size receiver - same weight, same stock specs, etc.....which is hard to do ( and 4 guns might cost me $16K )....vs $8K for a 12ga, a carrier barrel and 3 tube sets for 20ga, 28ga and .410..../ the Browning model I shoot with that spec is the XS Skeet model, no longer in production - ( now it's a 725 Citori Skeet ) same spec. ...
Having said all that ....looking for a used SKB is a good idea, or a used field grade citori or beretta...and with comb pads, changing recoil pads ...and using lead golf club tape - add weight under forend and inside stock ....to get the "fit" right .....and presuming your team has a coach --- they should be talking to you about all this stuff..../ and if they aren't find guys at your local skeet field that are shooting 24's and 25's consistently and talk to them....( don't take a lot of advice from guys shooting below 95 out of 100 )....if you're trying to shoot this game seriously..../ because as you probably already know ( even in windy conditions ) scores below 95 are out of the top 25% even in casual club shoots..../ ....with scores of 100 fairly common in bigger shoots...especially in 12ga or 20ga events,,,
Some of the local club shooters might be crabby old guys, like me, but they might help you out if you approach them right...and seriously, before you buy a gun --- talk to these guys, about guns / lots of us have a dozen skeet guns we've picked up over the years...and we might sell one to an eager young shooter...
Just don't buy junk.....