I talked to a technical rep at mossburg yesterday and asked , and he said DO NOT shoot heavy shot thru the facrtory x full  turkey choke. I was very surprised , but glad i called.  he reason was the chokes not upgraded and made for heavy shot. so not patterning the heavy 13, i'll just stick with the highbrass winchester double x  lead til i get a new choke for his 20 gauge.   i was told that the  heavy 13 patterns tighter than normal lead, not sure if it is true, but i will  pattern the carlsons mid range choke he has when I pattern the new turkey choke.
John