AZ: I can't speak to your choices as I've never seen the Hornady's used on elk(at least not the 154's).But I've used and seen used, the 140-160 gr 7mm Nosler Partitions on a wide range of game from the 7x57 to the 7 Rem Mag. I have precious few of these weights and styles that I've recovered simply because they pass through so frequently.
No need to spend a fortune on either one as you could work up loads with cheaper Sierra's(say),and substitute the Partitions for hunting.IME with the 7x57(22" barrel)you should be able to get about 2750-2800 with the 140,maybe 2600 with the 160(?).I'm guessing here because I never worjked with a 20" barrel.
There's a lot of historic precedent for these loads,as O'Connors wife, Eleanor used 160 gr Speers and Partitions from a 7x57 to kill a pile of African and North American stuff. Should do what you want, I think
