Of course the load used will differ with the use and the user's tolerance for recoil, which is significant in ANY single shot 12, even the fancy trap models.
I can tolerate a lot of shooting (say three rounds of trap) the "low recoil" 2 3/4" 1 0z. loads. For hunting, I use so-called "heavy trap" loads, which are 1 1/8 Oz. low brass, the equivalent of older 16 guage high brass loads. Needless to say, you don't shoot as much in hunting situations (except doves and ducks, which I don't hunt) and adrenaline is an excellent pain killer--I just don't feel recoil when shooting at game (well, I feel it the next morning.....).
High brass 12 guage, 1 1/4 Oz. and "short magnum" 1 3/8 Oz. shells I would stay away from with single shots unless you are especially recoil tolerant. A flinch won't help your marksmanship, even with a shotgun.
Unless you need a short stocked gun, I would also invest in a pullover recoil pad (I use the "Limbsaver" series, but have seen some neat leather-covered ones for a bunch more bucks). I have long arms and neck and need more "pull" than Savage provides anyway.
Buckshot and especially deer slugs kick like heck in single 12s. Sighting in slugs will induce a flinch in most people, no matter what they tell you. I would avoid them; get a deer gun with sights (they kick too, but at least CAN be sighted in!).
If you are thinking of using a 220 12 for defense, I'd look for some "low recoil" buckshot, such as that sold by Cabella's and others, or get some of the 1 1/2" "mini-shells" made by Aguila in Mexico, a Remington/du Pont subsidiary. At close range, they work fine and the recoil is light enough for a practice session that will leave your dentures in place. A 220 isn't anybodies idea of an ideal home defense weapon, but it beats the heck out of a dustmop! Even one 12 guage tube pointed at your belt buckle looks like the subway to Hell. Don't ask me how I know that.
