For the last 4 years I have been using the 85gr Gameking bthp in .243 myself. I have taken 7 deer. The only DRT shots where the one that was neck shot and one head shot. I don't generaly do head shots, but I thought the doe had been wounded by hunters on the next farm over, and all I could see was her head. The rest where heart lung shots. They never flinched, bowed up, or acted hit. None of them even bolted! They all walked about 10-15 yards and fell over. None exited, even the head shot! I don't recall any of them doing anything more than peppering the off side chest cavity! Don't expect this bullet to penitrate, especially at close ranges! The thing that has me worried is that they almost, without exception, left NO blood trail!
I guess I would call them effective, but I worry that if the shot isn't perfect that there will be no blood trail. I also avoided any kind of heavy shot with them, shoulder bone etc. I think they would fail if you expected them to have to penitrate very far.
Before that I had always used the Rem. Core loct 100gr. They nearly always exited and left a good blood trail, but I have lost a deer with these on two occasions at longer ranges. I think the .243 and the GK BTHP is an experts combo. By that I mean, you must disipline yourself, think about your shot placement very carefuly before pulling the trigger, and know the path the bullet must travel to make a clean kill, and don't expect to make ANY kind of raking shot! I,m not a fan of those any how.
After shooting a .243 for 20 years, I,m switching to a .260 and see how I like this round.