Quartering targets can cause problems with bullets skimming the edges for lack of better term. If you know the are quartering you can aim a little farther back to penetrate the vitals.
I once killed a buck at 435 lazered yards. I though he was slightly quartering away. I shot for a behind the shoulder shot. At the shot the deer ran head down straight off of a cliff into a ditch. The bullet " 140 partition out of a 7mag" made a very loud smack. I found the deer dead about 20 yds from where I shot it as it fell a long ways into the ditch. There was a circle about 10feet around the deer of blood. Upon gutting the buck I found no internal trauma to organs no holes thru the rib cage. Turns out he was quartering farther than I thought and the bullet had smacked the shoulder and traveled forward along the rib cage and thru the neck cutting the juglar vein and exiting the other side. Luckily his head was down or it might not of hit anything lethal. He was very dead but it was luck that I hit the juglar. Hence my apprehension for long shots on game. Things arent always what they seem at 1/4 mile away and the game can move a litlle in the time it takes for the bullet to get there. I know yours werent long range but I think maybe both of your bullets skimmed the edges of the vitals even thought the penetrated the internals. And like Mule Deer said the bullet did its most damage on entrance. I doubt a bigger caliber would of made much difference. Just a unlucky day. Nice Bucks by the way.
