I picked up a Jeb's Headhunter .555 locally and gave it a try in our little 870 turkey getter (21"). I tried some Hornady Heavy Magnum 3" 5's - results were unimpressive. Then I tried Federal Prairie Storm 3" 6's, with good results - sufficient at 35 yards and not ridiculously tight at 15. That's plenty of range for our hunting up here, so I'll carry this combo to fill my second tag.
(https://i.postimg.cc/0NfLgb3P/Jebs-35.jpg) (https://postimages.org/)
(https://i.postimg.cc/d1VgJJPd/Jebs-15.jpg) (https://postimages.org/)
(https://i.postimg.cc/GtBNszpm/870-20ga-turkey-gun.jpg) (https://postimages.org/)
I would probably search for a little better pattern.