I've had my 870 since 90's. Hastings non ported .650, .665, .670. Kick's .655, .665. MAD MAX ported, Primos Jelly Head. Nothing puts more shot in the 10" than Rhino 1st GEN. I found one on eBay, because dude sold the gun. I've never seen another used one and I check once a month.
I also have SumToy .660 I haven't had the chance to check it up against the Rhino. Hoping to do so in the next week.... But I've been saying that since Aug. I have shot it several times. just not at 40 with the hunting load..