I like/load 250gr Partitions over 59gr R-15
Are you sure that's your load--that's 6 grains over high book (Nosler #6). 59 grains is the listed max load for 225gr bullets.
As for me personally, I like 250's--why else would you buy a Whelen?? Here's mine with a cow elk from 3 years ago. The bullet was a 250gr Hornady: