NitroX has given you excellent advice.

I've seen a lot of eland shot over the years and although it must be said that a 375 or larger is probably a better choice, a 30 calibre (or even a 270 at a push) will do the job if you put the right bullet in the right place...... it could equally be said that a bullet in the wrong place, even from a large calibre, won't do the job.

As has been said, eland are bigger/heavier than Buffalo, however, they're not as tough as Buffalo and die considerably easier than Buffalo.