This photo is from a recent trip to Africa. One guy had a small scale so we weighed the bullets to see how much weight each bullet retained.
The first bullet is a 260 grain Partition. It retained 220 grains for about 85% retention.
The second bullet is a 180 grain Core Lokt. It retained 80 grains for about 45% retention.
The third bullet is a 180 grain Barnes Tipped TSX. It retained 177 grains for over 98% retention.
Take this for what it's worth. Each bullet hit different animals so it isn't exact science but might help out a bit. I certainly was happy with how my Barnes bullet performed!