My Jennings Buckmaster 2000 shooting 2117s/100gr wasps was underspined, and I never was able to get consistant groups with BHs and field points (I shot with this setup for a few years when I was just starting all the way up to two years ago). Thankfully I found this site, and was told about my spine issue, and was able to correct it (ordered a new set of gamegetters set to the correct spine, and voila!, my BH and field points were hitting VERY close (not perfect, but close).

Fast forward to this past winter. I ordered my CR334, knew I wanted to shoot Slicktricks (100gr), and with my DL and draw weight, I was a little in between the 3-39 and 3-49 range (I went with 3-49s), and my BH's hit very close as well. Neither bow was professionally tuned (my CR334 still isn't and I need Rob to walk me through some of that once I get new strings). So from what little experience I have with the issue, I believe it to be much more related to spine that broadheads (although I do agree different broadhead designs will exhibit various characteristics in flight).