I've used the 200 grain Speer/.300 Win Mag on several elk and one very large South Dakota bull bison. Worked just fine.
How was performance on the bison, if you don't mind my asking? How far was it when hit, did you recover the bullet, etc.? I'm considering using it in Africa on game in the wildebeest through eland size range so am very interested in your bison kill.
Inquiring minds want to know.
He was probably 125 yards away. Bison don't show much reaction to being shot, so I hit him twice in the lung area. He stood around for a minute or so, then finally fell over. The animal went right to the processor, and I was not able to recover the bullet.
The three or four bull elk I've shot with the 200 grain Speer were all less than 200 yard shots, and all were one-shot kills. I did recover two bullets. They both mushroomed nicely. I was using a max load of 7828 at around 2950 fps.