I have turkey hunted exclusively with my 870 SP 23" bbl for 15 years or better and patterned a few other 870s for my buds with different barrel/choke/shell combinations. I will tell you that every gun/bbl/choke/shell combination will shoot somewhat different in each "unique gun" regardless if everything is identical. The name of choke you settle on will ultimately be your personal preference, but the constriction and internal geometry will need to be tailored to not only the size shot you shoot (4,5,7,duplex,etc), but also the barrel length (23", 26", etc) and shell length (3", 3.5"). I hunted for years with a Kicks .670 GT and 3.5" Winchester HV #4s and loved my setup, but experimented few years back and I now shoot Indian Creek .665 with 3.5" Nitro H517T triplex and/or 3.5" Magblends (they both shoot almost identical in my setup). The one thing you can be sure of is each gun/bbl/choke/shell combination will shoot some different (pattern density, poa/poi, etc), testing is the ONLY way to find the ideal recipe for your setup. Another thing is if you find a choke/shell combo that your gun really likes, buy as many boxes of shells (sooner the better, exact lot # preferred) while they are available because you never know what will or will not be available next year. Best of luck with your quest!