The blood thing is weird and sometimes it just happens. As I say you should always follow up in great detail on your shots. I was with a buddy this year pushed a doe to him and he shot twice. When I got there he was throwing his hat and sticks proclaiming he missed. 50 yards later and maybe 3 specks of blood and a piece of bone, he had put a round from his 7X57 right through the shoulder and heart. Not sure why she didn't bleed and she was full of blood but she also didn't go far at all. I am not sure what bullet he was using but it doesn't matter. Every now and then one wont bleed. We spent probably 45 minutes looking very hard before we found her given we had no blood to go off of.
