Most turkey chokes I use or have run accross explicetly say not to use buckshot in them. I honestly don't know if it will hurt the gun/choke/pattern/you or not, but it must have at some point in order for them to put such a warning on the tube.

Everyone has what works for them, but it has been my experience that ultra tight choke tubes to not typically produce the best buckshot patterns at 35+ yards. By best, I am talking about tightest patterns here, straight up density. Out of one of my deer guns (I live in the part of the country where buckshot, deer and hounds have a lot in common), I get the best results with OO buck and an IM tube. The other gun is flat out lethal with a Patternmaster and just about anything. The PM doesn't have constriction at all, but rather just allows the shot to leave the barrel unmolested and strips the wad from the shot column. With the PM, my 870 will put 7 out of 15 pellets inside a 10" circle, and all 15 will be inside a 20" diameter circle. Pretty doggone strong for a buckshot gun. Much beyond 45 yards, buckshot loses its ummphh pretty fast, so while my gun is still able to put 3-4 pellets inside that 10" circle at 60 yards.... Its not enough to get the job done everytime.