A sling on a shotgun meant for turkeys or waterfowl is a simple thing. Unlike the one hanging from your deer rifle, it need only provide the means for carrying your scattergun so both hands can work a box call or set decoys. You are not going to "wrap up" in it to steady your aim. It has but one task--keep the gun on your shoulder--and you expect it to perform that job well. When it doesn't, when it slacks off and allows the thing entrusted to its care to dangle from your bicep, it's frustrating. Three or four times in a morning is maddening. Six or more can drive an otherwise near-silent hunter to shouts of profanity.
I try my best to avoid swearing at inanimate objects, and so I equip my turkey gun with The Claw from Quake Industries. This sling, as its name implies, grabs hold of your shoulder with the tenacity of a mountain lion reaching for its meal. Without the pain, of course. The Claw is actually more of a cushion, because it flexes slightly under weight and absorbs some of the jostling that causes a shotgun to suddenly hang below your elbow.
Quake says The Claw's pad is made from "durable non-slip polymer," but it's soft like rubber. Even when the temperature is below freezing, the material remains flexible. It's quiet, too, and it won't separate from the rest of the sling because it's molded around the nylon strap. The pad comes in three shapes for shotguns and rifles, including ARs. I like the "contour" version because it's streamlined but comfortable. If you're toting a heavy rifle, you might like the wider, more rectangular style better. There's also a thin, "slimline" version if you want to use The Claw as a hasty sling for support in field positions, although I've found the "contour" shape works fine for that as well. Yes, I have The Claw on several of my rifles in addition to my turkey and duck guns. Deer don't appreciate cursing any more than gobblers.