I am no nor will I profess to be a Elk expert. I have taken 2 witha 270 though and I used the 140gr Failsafe. I agree they are big and maybe the toughest animal to put on the dirt...shot placement, as well as a solid constructed bullet is a must. I personally wouldn't use a plain jane of the shelf ammo for elk, handloaded (bonded bullet) or a premium bullet (nosler part, a frame, barnes x or bear claw to name a few). As far as grain it would depend on the rifle and what shot the best, same with bullet style.

my neighbour lives for elk hunting and shoots a 280 with 165 gr Nitrex grand slams...it works very nicely and he has yet to lose an animal with this load. His shoots can range to tight or 300 yard plus. Personally I will be loading 160 or 175 grain parts next fall for my elk hunt out of my 7 rem mag. I would rather have the insurance of busting bone, then having to try and for sure place the shot in the rib. Oh BTW I am a good shot and have yet to not hit the vitals when aiming there....but I ain't going to chance it on my elk hunt...which I do every 3 years.

I would say let your gun dictate the round you load and practice it free (hand as well). do some research on the right bullet for the task in whichever gun you choose to tote. I am a firm believer of matching the bullet to the animal and have no problems switching for different game. Since for deer I only shoot BT's out of my 270 or 7 rem mag and love the results. But think it would be ignorant and stupid to say I won't change and hope that my shot was perfect to allow me to use the same bullet.

It's hunting the only thing we can do is be prepared for anything and everything. Success is usual that much sweeter when you have done your homework and it pays off...the fluke isn't the best avenue.