Your looking at several things, and the final answer is a compromise between all of them.
The smaller the shot, the more pellets, but the lower the penetration each one has (at any distance).
The tighter the choke, the further out you can hold a dense pattern, with all shot sizes.
The "tougher" the target (IE deer VS rabbit), the more penetration AND hit count you need.
So, what is the target, what is the distance, how are you choked?
BTW, for in house usage, you really don't need anything more than #9 target loads (at in-house distances everything including the wad will be inside a 1" hole), but you won't be punching through walls and endangering any family members on the other side
Thanks tailgunner. Main concern with shooting is just distance. Just looking at how far it will shoot - no real targets in mind other than paper at this time. As far as how its choked - no clue. Not as familiar with shotguns as I am with rifles and handguns in most calibers.
For pure distance, the larger the shot, the longer the range (downside is you reduce the # of shot available).
For pure distance, a slug would be your best bet (with the saboted ones having the advantage over the Brenneke type (attached wadding) which are better than the hollow base rifled type, which are better than the old "pumpkin ball" (single round ball) type.
As far as killing paper goes, you will have to try each type to see which one your gun prefers (BTW, the sabots really prefer a rifled barrel)
For deer, buckshot is considered a 50yd load, slugs are considered 100yd capable (a good rifled barrel with a sabot load it likes will reach out 125-150yd and still be effective)
you need to take shotgun out with a wide variety of ammo and pattern those rounds in your shotgun.. If you talkin a HD set up. Barrel length 18" or 20" your talking Cyl or IC choke. Agian need to bring out a wide variety of 00 buck and patten your shotgun. Some will pattern like crap, Winchester Super X from Walmart is one of those. Along with that Mil-Spec garbage from Olin. Cut them apart and they are identical.
Best HD 00 buck, Fed Low Recoil 00 Buck with FLIGHT CONTROL. Perform best in CYL & IC
My 20" Mossberg barrel is with my gunsmith, getting the forcing cone lengthened. this should really tighten up my shot pattern. I should have it back in a couple days. Range trip this weekend so I'll have some pics up, hopefully with inproved patterns
I've never needed anything more than full choke myself, I choose my shot size for gaing more range but sometimes on game you want to choose the next size smaller, that way you can put more shot on the target.
It all depends on what you're trying to shoot at a given distance. Don't expect anymore than 100yds with (buck, not bird) shot and that's pushing it
Not to hijack, but segue...Is there a difference between pattern if i use the same screw-in choke in a 18.5" barrel vs my 28"?
Can there be a difference on game....Yes
Depending on powder being used (especially for reloaders) a slower burning powder may not burn completely in the shorter barrel, thus giving a difference in pattern at a given range. (Not likely with store bought shells though)
The longer barrel can give you better balance, and sight plane when hunting and you will think there is a difference!
It's not easy going between the 2 lengths either when hunting. Hunting with a shotgun requires one to swing and follow through.....generally speaking.
Shorter barrels will get you a faster swing, and longer ones will be a slower swing. There are differences in sights and or vent rib angles too on different length barrels, some lower and some higher
Got a lot of my own questions answered.
Though mine is a Mossburg pump and I am very proud of it.
I was totally clueless about shot size and effect.
Right now it is loaded with #3 "heavy Turkey load" from Fiocchi.
Now all I need do is get out to bust some stuff up!
Im with prc77. In my experience with a combat shotgun having a 18-20 inch barrel and IC or C chokes you should be pretty effective and tight on a man sized torso target if using one of the "low recoil/reduced recoil" loads. These tend to hold tighter patterns due to lower deformation of the pellets upon powder ignition. The less deformed the pellets are coming out of the barrel the tighter they tend to pattern. The other thing I have noticed about the reduced recoil loads is that due to the slightly lower impact velocities they tend to penetrate deeper in to tissue as well. This also seems to be a result of lower impact velocities causing less deformation of the pellets on impact. Despite the lower velocities, these reduced recoil loads seem to be more effective at longer ranges as the patterns hold much tighter than the typical buckshot load. Might want to look at some "buffered" shot loads as well. The buffering material thats loaded with the shot provides some degree of cushioning to the shot on ignition and accomplish the same effect as reducing the velocities does. It may also still be possible to find plated shot in 00 buck sizes as well and this too will cause the shot to be a bit harder and deform less upon ignition as well as impact. I have found that while 00 buck can be quiet deadly out to 50 yards or so the shot pattern has increased to a point where only about half or less of the pellets impact a torso target at that distance making it a little less of a reliable fight stopper beyond 30-35 yards. Again these are just observations from me shooting various loads on civilian and military gun ranges over the last 30 years.
IMHO the HEVI-shot loads outperform all other loads that I have tried. Their Dead Coyote buckshot loads are second to none and their bird-shot loads pattern very nicely. They are expensive though. HEVI-ShotŪ 2012 Catalog
I have a 21 inch smooth bore rem choke barrel and with an extended rifled choke tube it puts rifled slugs into tight little groups at 100 yards. Same barrel with a light modified tube keeps 00 buck on a paper plate at 25 yards and on a 12" paper at 50 yards. Slugs open up to about a 12" group at 100 yards with that LM tube. Slugs are just the cheap Remington or Winchester foster slugs. It does considerably better with Federal premium slugs and most all the Brenneke offerings.