Many years ago, I read up on the Ashby studies, which still are arguably the largest source of information regarding penetration through heavy bone, specifically on Cape Buffalo. I think that everyone should realize by now, that this information wasn't really intended to be applied to North American game, where if you are encountering heavy bone, the odds of recovering the game are a little slim just based on anatomy. We can argue that point at a later date if necessary. I really only made this post regarding buff hunting.
I just want to share some of my experiences, and some from people that I know. I have said a few times that luck is probably the largest contributor to success when it comes to buffalo hunting and I still feel that way.
I guess I will go in a little bit of reverse order. I recently was on an Asiatic Buffalo hunt with a couple of outstanding hunters. We had some different experiences, which may be useful to someone else going on the hunt.
One of the hunters took a nice management bull and a cow, and the other took a nice trophy bull. Multiple arrows took one of the bulls, but only one went through a rib, and that one was around 1000 grains and tipped with an iron will broadhead. As luck would have it, the remainder of the arrows shot went between the ribs and had no impediment to penetration. All of us were using very high FOC arrows, I am not sure regarding the calculation, and all of the arrows were roughly between 900 and 1000 grains, being shot out of bows ranging between 70 and 75#. I know that my personal bow was 74# at 29.5" and was bareshaft tuned and shooting 926 grains at right around 155 fps.
I will describe my expereinces on 3 different animals regarding penetration.
The first was a nice management bull slightly quartering away at 17 yards. For a broadside shot, the ideal placement is up the leg and mid body to hit where the major vessels and airways go into and out of the lungs. This is reportedly the fastest way to put them on the ground. Since he was quartering away the guide said put the arrow on the crease and mid body. I hit exactly where I aimed, the bull ran up onto the flat, and to to my amazement the arrow fell out after 20 yards. The bull ran off with a scant short blood trail, and almost certainly lived. The arrow had blood spattered on around 4" of the shaft, and the Tuffhead broadhead was covered in bubbly lung blood. The guess is that the arrow was horizontally oriented on impact and tried to go between the ribs and got greatly slowed down to the point that only the broadhead reached the lungs, then it turned and fell freely out from betweeen the ribs. Surely if it broke ribs, it wouldn't have fallen out as easily, but obviously I can't prove that.
The next day was spent looking for that bull, and not finding it. Not surprising given the size of the lungs and the relatively small broadhead. As it would happen, a very large trophy bull was spotted and I was able to close the gap to around 17 yards again, this time completely broadside. Unfortunately, I hit around 5" below mid body, but straight up the leg. Double lung, but over the heart and below the great vessels of the lungs. The bull took off and we gave chase. I guess that there was around 23" penetration on this bull, with 10" of shaft sticking out, 20 inside plus around a 3" broadhead. Stopped on the offside shoulder. Dead animal, but he was able to make it past the escarpment, we lost sight of him and poor blood trail. We looked for him for 2 days and never recovered him. I was pretty devastated, and a combination of things, including my performance, made this my worst outcome hunting trip ever. This brings myto the next buff.
This buff was shot by the guide with a rifle after being mistaken for a wounded bull. I had the opportunity to put a couple arrows in it to put it out of it's misery. These were quartering away shots, with the bull laying partially on its side against the slope of the escarpment. The first arrow was pretty steep quartering away, penetrated well, but the bull didn't pass away quickly, so a follow up arrow was placed, slightly lower and less quartering. There was a loud crack, and blood poured out the wound. We assumed a heart shot but when it didn't expire rapidly, it was dispatched with a rifle. An extensive autopsy showed that the first shot went between a rib and destroyed the entirety of the closest lung. The second shot centerpunched a rib, and didn't get fully through the rib. The blood pouring out was from the damaged lung, not the heart. It took quite a bit of work to get that broadhead out. It was probably sticking a little over 2" through the rib but just tickling the heart.
Speaking of centerpunching a rib, a good friend of mine and great archer shot large mature cape buffalo bull and centerpunched a rib. Just enough to make him lay down a little bit away The follow up shot penetrated to the fletch and took him out. His first shot didn't quite make it past the rib. I think he was using high foc arrows in the upper 900 grains and around 77#.
I was using a similar setup with I shot my cape buffalo and was able to penetrate completely through one lung, but only tickle the other. He went a long way before expiring. Turns out, my broadhead hit him horizontally oriented between ribs, which acted like a brake on each blade, impeding penetration.
Cape buffalo cow I shot penetrated to the fletch quartering away, with a quick follow up broadside that broke thought the rib and took out the vitals. No autopsy on her as it was getting dark and the herd was threatening us.
Another friend shot a massive water buffalo quartering away. Shot went between the ribs, and it died quickly. He tried the same shot 3 times on the carcass, each time being stopped by the rib. When he shot it broadside he had full penetration.
Now some thoughts of mine based on these experiences:
Take the Ashby studies for what they are, but realize they don't include all hunting situation, specifically not quartering away shots on live buffalo. They also don't address the differences in anatomy of large mature animals from less mature animals, and what moving muscles can do to impede penetration.
I don't have enough testing to have too strong of convictions on things, but based on what I saw, you can't rely on the single bevel of a long 3:1 broadhead to rotate and crack the rib to improve penetration, particularly on a quartering away shot. It is possible that you would have improved performance with a shorter thinner broadhead in the long run. Another thing is on this last hunt I was using Tuffhead dangerous game heads. I really can't recommend that head. It is far thicker and a little wider than the 225 grain heads, and I think that impedes penetration more than a tiny bit of possible edge chatter would. Once again, I think there needs to be alot more testing particularly when it comes to quartering away shots.
I will leave off for now, just mentioning that the previously reported requirements for reliable full penetration of buffalo have been found to be inadequate under hunting conditions for myself and others that I know. If I am able to go back again, I will either use a more energetic setup with some changes to the broadhead that I am using, or I will limit myself to only what I perceive to be perfectly broadside animals, which is greatly limiting under spot and stalk conditions.