RE: shotgun slugs
Gonna have to buy several brands & put in some range time - it's the only way to know for sure what's gonna work. My scoped rifle barrel Rem. 870 shoots Lightfield 3" Hybrids the best - they kick like a raped ape, but shoot better groups than any other slug I tried. Even the 2.75" Lightfields didn't shoot as good. I've got my 870 sighted in for 2" high at 100 yds, but most of my shots are right around 50 yds.
My 870 didn't like the hypervelocity slugs like the platinums, hornandy's, etc. I'm told it might have to do with the slower rifling of the remington barrels...