Today, I went to the Turkey Shoppe in Edgefield, SC. They are the only place near by that has premium turkey chokes. They had plenty of Pure Gold and Indian Creek choke tubes. I looked at the those two for my shotgun and the IC was $85 while the Pure Gold in .670 and .660 were $65. I didn't think the IC could be $20 better so I went with a Pure Gold .660 choke. I already have some Win HV Supreme 3.5/2/#6's and am looking for some more shells to try before the season kicks off.
I really dont know if this would be comparing apples to apples but I have been patterning my 535. I am using the HeviShot .662 choke which is similar in diameter to yours. the only thing I could get to pattern decent with that tight of a choke was the HeviShot 3" #6 2 oz. I tried the HV Magblends and the winchester HV and it seemed to blow up the patterns. The best I got with the Magblends with a polished barrel was 138 in 10" @ measured 40. The Win hv was 98 in 10" @ 40 . The Hevi #6 gave me 191 in 10" @ 40. Hope this helps some.