well i just pruchased a 20ga project gun for my wife. ive come to the conclusion that finding a "cheap" choke that is hevi approved is really hard to come by for invector threads. ive already orderd hevi 13 in 7's and 5's, the chokes im considering are the hevi 13, pure gold 555, indian creek diamond strike, and possibly the cabelas hevi shot choke. any experience out of invector guns with these chokes? i cant afford to by them all, i already know that would be the "best" option :)
Any of the ones you mentioned should be alright. I'll bet there isn't a 10% difference in them.
You have got it nailed, except for the 5s. With the hevi shot #6 is good and I don't think you'll be happy with the patterns of the 5s, especially with the 20 gauge.
I am looking forward to your patterns!!
As for the "best" option, in a 20 gauge, it would be the PG .555 and the Federal Heavy Weight in 1.5 oz of #7