RE: is the 454 big enough to harvest elk
 

LOL

Oh ya it is way big enough!!
I hunt elk with a 270 every year one shot! As with bow hunting it is all about shot placement. All of my hunting companions hunt with 7mm mags, 300 mags and they tease me about my shot limitations; and yet I have shot an elk every year for the last 4 years in a row with my 270 before that I hunted with a 300 savage and did not have any problems there either but was usually limiting myself to shots 200 yards and under.
Practice practice practice, and you'll be fine...