I’ve been shooting sporting clays lately with my 12 gauge 28” barrel Winchester 101 and Briley extended choke tubes. I’d like to order a new barrel for a barely used older 20 gauge 870 Wingmaster and order some choke tubes for that one. What is the general consensus of the best barrel length for sporting clays? 26, 28 or 30”. Thanks.

Barrel length between an O/U and a pump doesn't equate to the same number...Because of the pumps receiver length...

For sporting most go with 32's in an O/U.

Barrel length is barrel length.
OAL is the variable.

More importantly, why are you moving down to a 20?

I'm with battue on this, with a difference of adding 34 inches to the common lengths, ie 32"-34" for an O/U. The receiver on a pump or semi adds around 2 inches. A 30 inch pump should handle similar to a 32" O/U, but weight distribution will differ a bit.

Overall length of the gun and where the weight is makes a BIG difference in fit and performance.
Gotta fit them and try.
Getting an 870 20ga to swing like a Win 101 12ga might be a difficult task. I see scores drop from such moves.
Or, if you care not about better scores, simply shoot what you like.

On a dedicated clays gun, I won't consider anything shorter than 32 on O/U and if avail in 34 - sign me up.

If using the pump, I'd go as long as I can get

Scores? This is shooting with the retired guys down here and I shoot with guys who are doing little more than making noise wasting shells. They have never even tried a sim pair yet let alone hit them and I need more of a challenge to help level the field. Muzzle heavier longer barrels might help with the follow through, so I’m thinking the 30, though the 28’s are more common and might be better at resale time. Either would be lots longer than the 101 with the 28 and longer chokes. I was trapping for a big sanctioned shoot last weekend for the guys with the Krieghoff, Perazzi and Kohler type guns and I didn’t see any short barrels.

The longest barrel length Remington made for the 20 gauge 870 was 28 inches.... weather the "X" frame (20 gauge on a 12 gauge frame) or the light 20 gauge frame.

I have a large frame 20 gauge (X) "left hand" with a 28 inch barrel I had choke tubes installed and new wood I use for shooting 5-stand, The sight picture between my Beretta 32 inch sporting and 28 inch 870 is about the same.

No doubt that 32” is the most common barrel length in a sporting clays gun today. However, that is a relatively recent phenomenon (last 15 years or so). That said, it is not a fad as manufacturers havre paid attention to what shooters are saying and doing and building gauche better - read lighter and longer, such that a smoother yet quicker barrel set provides an advantage on challenging target sets.

Shooters are better today than ever, targets are tougher, faster and more challenging than ever (made possible by wireless target systems).

The important thing about a sporting clays gun is that it be smooth (just the right mix of balance and inertia). I shoot 33” barrels that meet this criteria. I wouldn’t want the 30 3/4” barrels on my 1997 vintage Beretta ASE Gold backup gun to be any longer, as it is just right as it is (thicker barrels than those of my main gun). It all just depends, as it’s all in the feel.