To get immediately to the heart of the matter, based on long personal experience, I generally have little use for a shotgun with a barrel less than 28 inches long for hunting flying game (upland or waterfowl), or for shooting aerial targets ("clay pigeons"). You should also be aware, gentle reader, that while I personally own all of the common types of shotguns (side-by-side, over/under, autoloading and pump), I have a strong preference for SxS and O/U break-open type shotguns.

There was, for a while, a drift toward shorter shotgun barrels, but that fad seems to have run its course. The argument was that upland hunters typically did a lot more walking than shooting and a short barrel made a shotgun lighter and easier to carry in the field. This is true, as far as it goes. However, consider this: why spend the effort to lug around a gun that increases your likelihood of missing when the opportunity to shoot finally arrives? It turns out that, for most shooters and hunters, 28 inches is about the shortest practical barrel length for hitting the target.

This is particularly true for hunting and sporting clays guns of the break-open type, whether single barrel, side-by-side double or over/under, regardless of gauge. Break-open guns actually do very well with 30 inch barrels. I have owned a number of such guns with both 28 inch and 30 inch barrels and those are my favorite barrel lengths. 28 inch barrels are a bit easier to carry in the field and 30 inch barrels are a bit easier with which to hit. Either seems to work well for most purposes.

Break-open guns have very short receivers and thus are about four inches shorter in overall length than a repeater (pump or semi-auto) with the same length barrel. In other words, a double gun with 28 inch barrels is about the same length as a repeater with a 24 inch barrel. Keep that in mind before you order a break-open gun with barrels shorter than 28 inches.

I definitely prefer a 30 inch barrel for pass shooting ducks or on any sort of trap gun. Some trap guns are sold with barrels as long as 34 inches and 30-32 inch barrels are the most common lengths. This is because trap shooting is a long range game. Standard 16 yard rise targets are typically broken at about 31-36 yards and handicap targets may be broken as far as 45-50 yards from the shooter. The longer barrel allows more precise pointing due to its longer sighting plane and develops greater momentum for a smoother swing. The latter helps shooters to smoothly maintain the proper lead and consistently break targets. The same principles apply to shooting waterfowl at similar distances.

An experienced shooter choosing a repeater intended for very fast shooting, such as on the skeet field, might do well with a 26 inch barrel. Such a gun will still be a couple of inches longer than a double gun with 28 inch barrels. Skeet targets require very fast shots at short range with open choked guns and so do some bird hunting situations.

However, a break-open shotgun with 26 inch barrels will usually feel muzzle light and whippy. This encourages the shooter to stop his or her swing prematurely, which results in shooting behind the target. A short barrel also encourages "spot shooting" with a motionless gun, a good way to miss targets moving at all but the most gentle angles. A barrel shorter than 26 inches should not be considered for any wingshooting purpose, even on a repeater.

The specialized Turkey gun is a different matter. These shotguns fire pellet loads, but are aimed like a rifle at a bird on the ground and rifle length barrels of 22-24 inches seem to be the norm. Another specialized type is the slug gun. Slug guns are equipped with rifle sights and, like a rifle, fire a single projectile at a game animal. Some actually are rifles, with fully rifled barrels, built on a shotgun action. Rifle length barrels of 22-24 inches are typical for slug guns.

A 20 inch barrel seems about right to me for a riot gun, but it is definitely NOT a sporting gun and such weapons are not intended for shooting clay targets or any sort of game bird. Keep in mind that the shorter a shotgun barrel gets, the harder it is to hit with. I was once (innocently) nearby when a couple of LA cops, hiding behind a car parked at the curb in front of a bank, managed to miss a pair of robbers leaving the bank with several shots from their riot guns. This at a distance defined by the width of a city sidewalk!

Assuming that the shooter knows how to lead and hit moving targets, the key to scoring with a shotgun is stock fit, sighting plane, gun balance, a smooth swing and follow through. If a lot of shooting will be done, as in clay target games, muzzle blast and recoil play an increasing important (negative) role. Short barrels have a deleterious effect on all of these except basic stock fit.