I shoot a 12g rem 870 WM with a 24" hastings paradox cantilever rifled barrel (1:34 twist)w/a aimpoint red dot sight up top. From my experience i shot about $160 worth of ammo from a bench rest to find the tightest groups,I tested; 2-3/4Rem core lokt ultras, 2-3/4lightfield ids, 3 lightfield exp, 3 win partition gold, 2-3/4win platinum tip, 3 brennekes, 2-3/4hornady sst's, 3 federal barns expanders, 3 and rem buckhammers, 3 rem copper solids

The tightest groups produced @ 50yds was from the buckhammers, i could lay 5 slugs on a silver dollar, the copper solids were the second tightest, tied withthe brennekes. EVERYTHING else was crap, shooting 6" groups on up @ 50yds,, i think its due to the higher velocites an my barrels 1;34" twist rate, the SST's were the worst, as they had fliers everywhere, let it be know that ifyou are going to shoot the new ultra high velocityslugs, your rifled barrel best have a 1:28" twist rate or you wont stablize thebullet. buck hammers are a great slug that can reach past 100yds. its zero is at 100 yards and theycarry LOTS of energy. just my 2 cents