Id strongly suggest you may want too spend some time running on a tread mill or stadium steps with a heavy back pack (40 lbs min),
doing so at least 3-4 times a week, for at least an hour a day,
and spend as much time shooting your rifle from sitting positions ,
and practice shooting prone behind your back pack as a rest, with a sling and a bi-pod
the time spent, doing so, is very well invested...there are no bench rests in the field

this is not my 340 wby, pictured below , but it could be a clone its so similar,
what caliber rifle you select is FAR less important than your ability to hit where your aiming from a rapidly acquired field position,
A high degree of confidence and familiarity with the rifle you carry is a huge advantage

youll almost never see an opportunity for a similar shot out in the open, like these pictures,posted below, which were probably taken in a national park or some non-hunting area




my late hunting partner considered anyone not equipped, with a browning BLR in caliber 358 win ,
while hunting elk too be hampered and working under a sever dis-advantage
I loaded for him for almost 30 years , fed 215 primer, 250 grain speer and 44 grains of IMR 4064
that carbine accounted for at least 14 elk over 35 years.
.
he constantly referred to my 340 wby as a "damn CANNON"
we were both successful.