I'm with Miles on the Rages, I prefer the rubber o-rings. I use the Rage replacements, they are cheap, come in a quantity, and easy to change out before season.
I don't "think" I've ever had one open on the bow or the crossbow.
I used the NAP Killzones with small diameter arrows and they were very effective. The blades seemed very secure, and left very good blood trails.
