I started using NAP Spitfires last year. Took a nice doe, but was kind of unimpressed with the penetration. My son Steve put a good hit on another doe using the Spitfire, but did not appear to get good penetration, and was unable to recover the animal. He recovered the arrow and found only two of the blades had opened. On opening evening this year, I had a 20 yard quartering away shot at a doe. The shot was true, but when she blasted off I noted the arrow flopping around, with minimal penetration. I found the arrow about 20 yards from the point of impact, blood only a couple of inches up the shaft, and NONE OF THE BLADES OPEN! No blood trail, no recovery. Disgusted, I switched back to my old standard NAP Thunderheads and took a nice 6 point the following evening. Great penetration and blood trail, the buck only went 50 or 60 yards. I' m using 100 grain heads, shooting a 64 pound pull, and generating 230 fps. Has anyone else experienced this with Spitfires, or am I doing something wrong?