Have a 20 gauge benelli that doesn't always cycle with 2 3/4 shells. Went to 3" with the idea that more punch will help it cycle and not jam. Also, thought more pellets will be better. But now have heard that 3" don't always pattern well. Has there been any studies done on patterning and shot string? Thanks for any info.

I'm not sure that switching to the 3" shell will solve your functioning problem, but simply shooting the gun will tell you that. However, Benelli should get an opportunity to make the gun "right" as it is supposed to function with any shell it is designed for.

As to patterns, it is true that the longer the shot column, the less effective the pattern (generally). By definition, the shot column of a 1 1/8 oz load in a 20 gauge is going to be longer than the same load in a 12 gauge, so the same load is generally regarded as slightly less effective in the 20 than in the 12 gauge. But what you are interested in is how the heavier load compares with a lighter load in the same gauge. Although shotshells can behave in peculiar fashions in certain guns, with one manufacturer's load patterning better than another's even though the velocity and weight are the same, you should get just as effective a pattern from a 1 1/8 oz 3" load as from a 1 oz 2 3/4" load -- but maybe not more effective. In other words, if you are seeking an effective 20 gauge pattern that you would get from 7/8 oz or 1 oz of shot, then the three inch 1 1/8 oz (or heavier) load will do just as well in the same gun. Of course, you'll pay for it in both more recoil and more expense.

Stonecreek is right in what he says about the general ballistic tendencies.

What kind of hunting (species and distances) are you going to use the 20ga for? This will usually dictate if you need to move up to the 3" shell.

To me the 2 3/4" w/ 7/8- or 1-oz. loads will handle most 20ga upland duties (dove, quail, etc.) but when I'm shooting ducks or pheasants I normally shoot 3" loads. Why, because the 3" affords me more room for the larger pellets (especially steel) that tend, I feel, to work better for these species.

Of course, I pattern all of my loads and chokes to make sure they maintain good pattern density at the distances I'm using them.

Good luck.

bob brister wrote a book,SHOTGUNNING THE ART AND SCIENCE (?), where he did a lot of pattern testing that was real interesting. he made a large moving target which his wife drove at known distances and speed while he shot at it. the loads he used may be dated but it gives you an idea as to how the pattern developes and its terminal look

There are a huge number of loads available so you must ALWAYS pattern them. Don't make assumptions or go by a table , you might get a surprise ! Steel shot with my Benelli gave EXTRA, EXTRA FULL pattern with mod choke ! Benellis do run tighter chokes than most.
Benellis also like heavier loads. Like rifles shotguns need what they like which is not always what you like !

Yep, just get some of our favorite shells and and give them a try at the pattern board.

Here are a few numbers from my 20ga to give you an idea of what you might get with steel loads if you are looking for waterfowl ammo.

Citori w/ 28" Invector-Plus barrels and Briley flush chokes (patterns average of five, 30" post-shot scribed circle, yardage taped muzzle to target, and in-shell pellet count average of five).

Federal Classic Steel 3" 1 oz #4 steel (186 pellets)
30 YARDS
IC / 150 (81%)
40 YARDS
IM / 127 (68%)

Remington Nitro-Steel 3" 1 oz #3 steel (152 pellets)
30 YARDS
IC / 131 (86%)
40 YARDS
IM / 114 (75%)

Remington Nitro-Steel 3" 1 oz #2 steel (118 pellets)
30 YARDS
IC / 105 (89%)
40 YARDS
IM / 99 (84%)

Good luck.