I have a 870 with a Improved cylinder barrel. My question is what kinda accuracy should i expect out of it and, what would be the farthest distance it should shoot decent groups. I have never used slugs and, i just thought i would give it a try this year. It shoots buckshot pretty decent out to about 30yds. Also, whats the best slugs to use with this setup?

I don' t hunt with a shotgun but I had a 870 a few years back and it came with 3 chokes,one was a rifled choke,so I figure I would have to try it out while I was zeroing it with a scope for turkey season,I shot the Federal sabot slugs,zeroed for the turkey load I shot the sabot slug with the rifled choke and it hit dead center at 50 yds tried 3 more and they stacked in the same hole at 50 yds.
Thats as much as I know about the shotgun slugs.

I assume that your barrel is a smooth bore verses a rifled bore, if that is the case use foster type slugs and rattle a few out at a target. Try different manufactors as your gun may pattern one better then another.

i have one and it though slug all over the paper and my uncles does the same but he got a deer with it (lucky) i bought a smooth bore slug barrel for mine ad it does a decent job ( If i remeber right its been awhile) the only thing is it shoot way low and to the right but thoughs a nice group oh it a 870 express 20 ga