the highest energy BY far that i've seen at the muzzle and up to 25 yards or so is the 3 1/2 inch Lightfield Slugs. Their Commander IDS is 465 grain at 1900 fps. thats HOT. Over 3700fpe at the muzzle and near 2600 at 50 yards.
They have a new IDS Plus ammunition line for 3inch and 3 1/2 inch 12 gauge that shot a 600 grain slug at just over 1700 fps for the 3inch and near 1900fps for the 3 1/2 inch. That translates into like 3850FPE at the muzzle for the 3inch and over 4700FPE for the monster 3 1/2 inch! Cant really find more info on that at this time but that amount of energy is STAGGERING!! 458 win mag performance at the muzzle but it does slow down to like 1700fpe at 125 yards.
3inch Lightfield Hybrid Elites. 546 grain at 1730fps. 3628 fpe at the muzzle. over 3000 at 25 yards, 2500 at 50 yards.
Probly the best overall performance load that holds higher energy and flat shooting out 50-150 yards is the 3 inch Winchester partition golds. even the 2 3/4 inch is a hefty load. the 3inch load will give you 385 grains at 2000 fps and make 3400fpe at the muzzle, 2867 fpe at 50 yards, and almost 2400fpe at 100 yards. Still over 2100 fpe at 125 yards. Thats like an 30-06 at 100 yards energy wise but with a much bigger bullet. the 2 3/4 load still gives over 3000fpe at the muzzle and 2100fpe at 100 yards
Remingtons 385 grain core lokt load at 1900 fps is similar to the partition gold in performance.
Winchester also has a platinum tip that is a 400 grain at 1700 fps. 2566 fpe at the muzzle but it makes a good 1800 at 100 yards. This is what i use and its very accurate in my 870 super slugger. great expansion on deer sized game
For longer ranges out to 150-175 yards winchester makes a new 300 grain sabot that moves at 2000 fps as well. not as flat or as powerful as the 2 3/4 inch or 3inch partition golds but probly easier on the shoulder.
they say its accurate too.
Buckhammer is a stout load too tho. The 2 3/4-incher is a 1500-1550 fps, 1 1/4-oz or 546 grain load that generates 3,200fpe at the muzzle. thats all i could find on that load so far. the 3incher would be a stout load with 600 grains or 1 3/8oz and probly closer to 1650-1700fps. Pretty like the Lightfield IDS plus slug but doesnt shoot as flat i would think since its less aerodynamic
And last but not least, for BIG game where a HARD cast lead bullet for deeeep penetration is necessary...look for Dixie slugs. they shoot some of the largest/heaviest slugs on the market today. 600-730 grains. not as fast as the others and not as much energy but they do have alot of energy to get most jobs done. They have been used on cape buffalo and such with good success.