I had a big lesson on momentum and penetration when I first started shooting carbons. I just couldn't get over the speed and "straight to the target" zip of light arrows. Going from wood shafts to lightweight carbons was like stepping up the plate with a rifle in my minds eye. Zip, and the arrow was in the target! I was shooting a 53# pronghorn with carbons and a 125 grain wensel head with an aluminum adapter. Total arrow weight was less than 400 grains at best. I had been shooting cedar up to that point and had taken a few deer. Beginners luck I guess.
My first lesson came early in the season when a group walked by my stand at about 15 yards. I picked the last animal in the group and took my shot. Good location right in the boiler room, but with a full 5 inch penetration... I was sick as I watched white flags bound over the hill, one with my most of my arrow sticking out the side. I spent the rest of the day and into the next trying to locate her. She went over a mile and a half before she retired, but I was lucky enough to actually recover this animal. The coyotes had gotten there first, however.
I didn't change my setup, just blamed it on hitting a rib, or bad luck, whatever...
Later that same season, my brother was down as was Charlie Lamb. I had a forky that kept walking by my stand, he did it four times and finally I said to myself if he does it again, I am putting meat in the freezer. The fifth time he walked nearly under my stand. I drew back, and leaned nearly 90 degrees over and took my shot. I had practiced this many times, and felt confident. Location was good, but again I watched the animal bound away with most of my arrow sticking out of it. This one was never recovered. Steep angle and no exit, no blood trail. Pneumothorax and most certainly fatal but no recovery.
Lamb asked me how heavy my setup was after helping me track most of the day unsuccessfully. He suggested I was shooting way too light a setup.
I was really, really dejected and felt like a slob hunter. I didn't hunt the rest of that season. Didn't deserve to..
Next summer I did a lot of research. Worked over some numbers with basic potential and kinetic energy with the physics teacher at the high school I teach at. Upped my setup to 650 grains. Brass insert, steel adapter and the same head. Practiced, practiced, practiced.
The result: Two deer down within sight of my stand. Both complete pass-throughs. I have continued to shoot this setup ever since and have had pass-throughs on all but one animal since.
Bottom line for me: There is NOTHING worse than the feeling of dishonor and dejection that comes from wounding game. I will do everything in my power to keep that from happening again. The two biggest components for me are practice and having a perfectly setup arrow. That means 10 grains per draw weight minimum, bare shaft tuning first, lots and lots of practice, and a clear quartering away shot within my 20 yard comfort range. Any of those factors are missing, and I am taking a picture instead of processing meat.