My dad shoots 3" Copper Solids with his 11-87 SPS w/ Cantilever barrel and monte carlo (raised comb) synthetic stock. He is good to 150+ yds. with them. Out at that distance he holds at the spine to drop into chest. The reason for more knock-down power with copper solids is they have 100% weight retention.

I have an 870 Express Slug gun with 23" Cantilever barrel and monte carlo synthetic stock, but I shoot the Hornady SST's. They cost so much so I haven't shot enough of them to see how well they group, I shot enough that I know I will hit the deer. With the longer barrel and hornady SST's, I am good out to 200+ yds.

I would try the Copper Solids in 3" or the Hornady's (if you can find them, they are rare because everyone buys them up if they find them). I have also heard nothing but good things from people that shoot the Federal Barnes.