I wouldn't say that it would be too small depending on what load you used but it will be too illegal in many states.

I wouldn't go after elk with a 180 grain ML bullet of any kind. If the 45 is legal in your state then I would highly suggest bullets like the 285 Hornady Great Plains or buffalo bullet, 250 grain precision sabots or just about any of the PR conical bullets, or 275 grain power belt.

A;so take into consideration that 50 caliber "stuff" will be much easier to find, usually cheaper, and offer much more choices in accessories and rifles.