I was shooting today and decided to screw on a 100gr Grim Reaper expandable. At 20yds I'm about 6" rt and about 4" high, and the arrow seems to wobble realy bad in flight.I shootleft handed. When using my 100gr field points I'm grouping 5 out of 7 arrows inside a 3 1/2" black dot I painted on my target. The arrows seem to fly ok. Any ideas as to the problem? I haven't papertuned thebow yet.