I been shooting feathers for the past 12 years and in my experience they do effect a fixed B/H down range. Out to 20 yards my groups are the same but beyond that the POI change with my Muzzys. I'm using 4 inch feathers for hunting.and 3 inch for target. I can't say what a mech. head will do but I think it depends on the type of mech. head your using Iwould think. I got cought in a down pour yesterday at a shoot and with field points I don't see any effect. The hardest part is seeing the target in the rain. I also have a Cat quiver for hunting because of my feathers. They are a bit of a pain sometimes in bad weather but they fletch better then vanes for me and are a little more forgiving. Plus for the most "important" part they look reallllly cool. I like the powder for weather proofing because it keeps the feathers pliable where the spray's stiffen them up some. Jerry