I do load my own buckshot with BP wads, extra hard #4 buck, with Copper BB's in the middle of the stack, filled with BP filler in an Active hull, 1 5/8 oz pay loads at 1300 fps.
Truthfully, I get extremely good patterns with factory Buffered, Copper plated #4 buck in 3" mags with 41 pellets.
The Hastings Turkey choke and Carlson's turkey chokes out of my 11/87 and Mosburg 500 pattern so tight that they are worthless except for longer shots. The worst of these two chokes will pattern 20" at 40 yards wtih F,and #4 Buckshot, the best patterning 15" or smaller at 40 yards. The Hastings Turkey will pattern the Rem 3" 00 and 000 between 12-15" at 40 yards.
The cost of buckshot is so high, some of you guys ought to investigate the possibility of loading your own using BP products. They have the wads, hulls, buffer, and buckshot. You will also have the option of loading F Buck, TT shot, T shot, and BB's which kills heck out of yotes long ways out. A used Mec Sizemaster can be had for cheap off of ebay.
I have patterened a lot of shotguns over the years with fixed chokes and screw in chokes with standard factory 3" and Home made buckshot loads. Brownings Pump shotguns pattern very tight for their choke as a general rule with #4 buckshot; Rem 870's, 1100's, and 11/87's pattern buck shot tigher in full chokes and even tighter with Extra full and Turkey chokes.
I can't emphasize enough that you shoot more than one pattern with a load. One pattern may be great, while the next will be crap. All you have to do is stick up a piece of newspaper at 40 yards and shoot for point of impact and pattern.