Dnk, All of my elk have reacted differently.My first wasa bigcow hitin the liver (passthrough)-it went about 1/4 mile and was still alive an hour later when I found it (another arrow through both lungs and she was dead in 3 seconds). My second hit the "elbow" on another big cow and just deflated one lung. She would not go down, even after I got 3 arrows into her, until I finally got the other lung. My third was a spike bull that took out both lungs and the BH made holes in both sides, entry was right above the leg (barely missed the shoulder bones) and exit was right at the seam where the neck meets the shoulder on the off side. He ran 70 yds and fell over dead in less than 2 min., maybe less than 1.The next was another big cow that was hit too far foreward. Fortunately, the arrow took out the trachea (windpipe) and a big blood vessel right beside it- probably the corotid artery.The vesselwas big enough that I was able to stick my finger into it. She made it about 45 yds and fell over dead (much to my surprise after seeing where I hit). All of these were shot with a 50# recurve.The first one was with a 2 blade stainlessbear BH. It didn't hold up as well as I would've liked so I switched to the Zwickey after that.My nextelk (another cow) I didn't recover. It was when I first started hunting with a crossbow and I was using a "lighter" (only 500 gr.) bolt. The hit looked perfect as far as placement, but only penetrated about 5" or so, just one lung. I'm thinking I must've hit a rib, it was too far back for the shoulder bones. I never found the elk, but I know it travelled at least a mile on one lung.The lastone I got was acow (2005). Itwasalso shot with the crossbow and a beefed up (heavier) bolt. It took out both lungs and she only made it about 70 yds. Elk don't last long without lungs but they can make it a long ways with one strong one. Penetration is king and, in my experience, weight (that is, bolt weight)= penetration. This year I hope to draw a bull tag. Even after chasing elk around for years, I still haven't gotten a bull. I've had a few close calls, but still don't have that big 6x6 up on the wall. Hope this help and sorry I was so long winded. Grndhntr