You will really like them, I use them on elk and back off a bit to 260 grain Nosler HP's for deer. There is no doubt in my mind the 300 grain XTP's would be very adequate, but I all the confidence in the world with the partitiion. To often I have stripped the lead right out of the copper, but with a partition no concern. I will post the recent results from a shooting trip with an inline in the next couple days. I was shooting .458 (45-70) 350 grain RN bullets from a 50 cal A&H, 3 of the six bullets that I recovered mushroomed just like you would want. 3 others I found the copper was all mushroomed out, but no lead - the lead had continued into the sand pile. Had it been an animal - it would have been dead, but if I were to shooting Noslers I know a majority of the bullet would have remained intact and continued to penetrate.
They also group great, I do not have ballistics on the Nosler from a sidelock yet, but from the inline I am getting great velocity across my chrono.
Good luck