RE: Deer Aren't Dropping
I'll assume the bullet your using is the Seirra Gameking BT? If so this bullet performs better at longer distances, the gamekings have never had a rep to be real solid as the jacket is very thin. What is happening is due to velocity the bullets is over expanding, maybe even fraging to bits and not producing a exit by lack of rentention which equals penetration. I used the seirras for one year a long time ago, like you I was in love with their accuracy. My buck was no more than 30 yards and the bullet exploded into bits with no exit or opposite side damage besides a few bone frags in the opposite ribs. This buck travelled 100 yards the blood trail was thick at the intial shot location than tapered to a drip or two...thank good for snow! He had one lung into soup and the second looked partial and blood shot. The doe was 150 yards and the bullet performed flawlessly, leaving a nice sized exit hole..she still ran about 30 yards but was dead on her feet the lungs were torn apart. This was with a 270 win 130 gr bullet. Now mind you this isn't a lot of real field data, but it was enough for me to switch and never look back.
Being your shots appear to be 100 yards or under I would either move up to the 180's or switch to a bullet that is more solid constructed. A 165 Nosler Partition would be a good place to start, I have found them to be quite accurate and they will exit any deer you shoot broadside!
As far as bang and flop, that really is a uncontrolled occurance on a rib shot, some do and other do not, but you take out the lungs and he or she is walking/running dead.