I cannot speak to the terminal performance of the 180gr I can only say they are a very accurate bullet. The 165 Gameking on the other hand I have EXTENSIVE experence with. More deer then I care to count all 1 shot kills, all died in 20 yards or less and all shot through and through reguardless of shot angle. A very good bullet it is in no way too soft IMHO. While I use the SP version I understand the HP is even tougher (thicker jacket) the BC kinna sucks but inside 200 yards that won't be a deal breaker.
SGK's was where I started. A wise man told me that when accurizing you rifle remove as many variables as possible and he went on to say "use SGK's as they are great accurate bullets", and indeed they are.
I then used these as my hunting bullet. I have had bullet failure twice with 180gr SGK's (2 620fps) , considering that I had only shot 6 animals with the SGK's that makes the failure rate 33%. Now before all you SGK boys go ballistic .....
Failure 1 - was a frontal shot on a Kudu bull at about 45yds. The Kudu ran 40yds and dropped. The bullet punched a 1" hole into the chest and then totally disintegrated. Most the internal organs were liquidized and on dressing the animal is was an absolute mess, blood gore and bits everywhere. Now although the bullet "failed" it accounted for the Kudu in short time so it was very effective. We were unable to recover even one piece of the bullet on slaughtering.
Failure 2 - was on an Impala Ram at 20m. The ram was quartering away from me, I aimed for a spot at the back of the rib cage. The bullet entered the skin, deflected off the ribs and travelled between the ribs and hide, it then left the shoulder and re-entered the animal in the neck. Clearly the angle was such that it caused a deflection which probably could have happened to any bullet in all fairness. A second shot was required.
Here is the bullet in question.
These two "failures" and I use quotation marks on purpose, caused me to move to a bullet that I felt had a better construction and that would hold together better when bone was encountered. I have no doubt that SGK's and Pro Hunters kill and kill effectively, I just prefer a cleaner entry and exit wound.
Since changing over I have not had a bullet failure, Kudu taken on the shoulder have a calibre sized entry wound and a maximum of 3/4" exit wound. Most bullets pass through when on the shoulder. I have only recovered one bullet and that was from a Blue Wildebeest, a shoulder shot at 225yds and the bullet had lodged under the skin of the opposite shoulder, perfect mushrooming. I did not weigh the bullet as there was a youngster with us who was desperately eyeing out the bullet which I gave to him.
More recently I bought a 6.5mm Swede for my grandbuddies to hunt with. As is my practice the first bullet I buy when settling in a new rifle is a Sierra. In this case I bought some 120gr. Pro Hunters to download a bit for the little guys. After getting the rifle sorted out I did not have time develop a new load with the my bullet of choice, Accubonds, so we hunted with the 120gr. Pro Hunters. The two each shot a young Impala Ram, both shoulder shots, meat damage was not however excessive and the exit wounds were in the order of 1.5". This further convinced me to keep with the Accubonds which I have subsequently hunted with, the results are better.
So while being a fan of the Sierra's I settle my rifles in with them, if I had nothing else I would hunt with them, but I prefer to use something else when hunting to remove as much risk as possible.