Power

The problem bullet makers have is designing a bullet that will perform well from 50 yards out to 500 yards. With super-fast velocities at close range they have to make their bullet tough enough to hold together. At extended ranges the bullet is flying much slower (sometimes as slow as 1500fps or slower) and won't expand as muchso it's hard to make a bullet that will perform well at both extremes.

I'm guessing that due to the range and possible lower velocity of the bullet when it reached the elk it didn't have quite enough energy and velocity to open up as well as it could. Thus the bullet travels right through the animal and out the other side, wasting some of it's energy on the ground beyond. That's the game you have to play when you hunt, is picking a bullet tough enough for a really close shot or a quartering shot where you have to pass the bullet through more of the animal than say a broadside shot. Failsafes are a very tough bullet and will hold together under the harshest shot so a broadside shot will do little more than punch small holes through.

If you consistently take a 300 yard shot at broadside animals you might want to check out some other bullets. The Nosler Partition is a good bullet as it's soft in the front for good expansion at long ranges but also has a partition in the rear to hold together in case you have a closer shot. I've used them and they work well. I've since switched to the Nosler Accubond but haven't had a chance to shoot a deer or elk with it yet so I can't comment on how it performs. I think it'll bea good round for deer and elk and black bear (my primary 3 species I hunt with my 7mm Rem Mag).