Well lets see here. i dont have grim reapers nor have i heard anything about them good or bad. i do have the scorpions. i was very skeptical about mechanicals. i got them as a gift so i had no choice in it. i did much testing here at my place to make sure that they opened and penetrated. after my research i found that they open EVERY TIME. they also penetrate quite well. they went in both my targets the same as my golden key dead heads, but my nuge blades beat the dead heads and xp's. so i say that the xp's are very dependable.