FWIW...the guy who has probably shot more trophy lions than anyone alive has used a 375 RUM (300
2750ish, IIRC) on most of them.
Last year I followed the vultures in to three problem lion kills and I thought the 3/8" hole in the end of my 375H&H looked awfully small! These lions were just out of a park and I had been warned they didn't have any real fear of humans...especially when humans disturbed their dinner!
Next time I will take a 416 Remington or maybe the 375 Weatherby (300
2700ish) I just built.
If you can stomach the Ruger, I'm sure it would work also.