well I shot an IC BDS out of an 870. 3.5 inch 2 oz copper plated #6s putting and average of 136 in the 10 at 40 yards with a dirty barrel! I know guys shooting them from mossbergs, remingtons, benelis and none of them have claimed they suck. most of them did not get the best results from the first shell/load they tried either.
you might have an un-uniform FC (forcing cone) it might be just because your barrel is dirty. you really owe it to IC to do a thorough test before you bash them. your gun no doubt is in need of a deep cleaning and polishing. this will help patterns substantially. your gun might not like that constriction. or those loads. there is just to many variables, most of them you neglected, for you to be able to claim that IC chokes are a fraud. you will likely go through a lot of chokes to find the best when you have your mind set on one load.
out of curiosity lets see some pics of your patterns. was the pattern centered on the turkey head?