I started using Grim Reapers last year and have been happy with the results. Shot two yesterday, both pass throughs but noticed the blades were closed. I was a little worried the blades weren't opening until I watched this. Pretty cool. I didn't know the blades closed as a result of inertia after exiting the deer.
https://www.youtube.com/watch?v=qZOnwNS_cPw
https://www.youtube.com/watch?v=qZOnwNS_cPw