I wouldn't worry about what the guide's recommendation, because it is just that. Go by what the hunting regulations in NM say you can use, that is all you need to really worry about. I used the 150 grain Nosler Partition to kill all my elk in my .270, however I wouldn't be afraid with any 130-140 grain Partition, TSX, GMX, E-Tip, or bonded core bullet.
If the guide is doing his job properly he is going to take you out shooting before you even go hunting. He'll make sure that your rifle is zeroed and he'll get a feel for what kind of shot you're going to be able to make. As long as you show up and your rifle and you are shooting well, that will make the guides job easier.
You have some time to get things in order, just spend your money on practice rather than a new rifle. I'll bet you'll be eating elk steaks back home if you take the .270. Just don't sweat the small stuff, work on accurate shooting from field positions and getting in really good shape since it looks like you are close to sea level and altitude is no joke.
If the guide is doing his job properly he is going to take you out shooting before you even go hunting. He'll make sure that your rifle is zeroed and he'll get a feel for what kind of shot you're going to be able to make. As long as you show up and your rifle and you are shooting well, that will make the guides job easier.
You have some time to get things in order, just spend your money on practice rather than a new rifle. I'll bet you'll be eating elk steaks back home if you take the .270. Just don't sweat the small stuff, work on accurate shooting from field positions and getting in really good shape since it looks like you are close to sea level and altitude is no joke.