All you guys asking about which slugs shoot best...
 

My results are in:

*it IS granted that each gun will do its own thing*
-870 magnum reciever with pre-1999 hastings fully rifled cantilever scope barrel.
-I tried, (all were 2 3/4") R. Buckhammers, R. Coppersolids, R. Core-lokt, F. Barnes EXpanders, F. Vital-Shok, and W. Super-X.

My gun showed a definate preference for both/either the Federal loads. At 50yards both gave nice cloverleafs. The Vital-shoks interestingly grouped high 2" and right 1" compared to the EXpanders. All others made dissapointing 3-4" groups.
It was 70 degrees with a light unsteady breeze. Gave the barrel a good cleaning before the sesion and then fired 3-shot groups. I sent one patch of solvent between each 3-shot group bollowed by 3 or 4 clean patches and then ran only a brush down the barrel a couple times between individual shots.
I will buy some more buckhammers though. I don't have any fears of them fragmenting and they entered with nearly twice the hole and left with twice the hole compared to how the others treated a 55g drum. They're 2/3 the price in my area so I may play around and see if I can't get the 3" or managed recoil versions to work.

Conclusion. My 870/Hastings like both Federals, everything else it merely sent downrange without unbearable slop. Buckhammers gave the impression of great old-fashioned terminal ballistics. (Noticeably more recoil too;) ...and yes, I realize deer are not made of two thin sheets of metal.)

RE: All you guys asking about which slugs shoot best...
 

Thanks for the update...
c7