I have killed one elk, a couple antelope and a deer with the Barnes TTSX 180gr out of my 300wm. What makes Barnes and other monolithic bullets good is their weight retention, which translates into penetration. When a monolithic bullet hits bone it will hold together much better instead of exploding like most lead bullets. With all four animals, I saw great terminal performance, and none went more then a few yards.
However there are a couple things to think about when using Barnes. Barnes bullets are 100% copper making them softer then most jacketed bullets that use a gilding metal (95% copper and 5% zinc). This will cause greater copper fouling in your barrel. This can be a real pain to clean, and if not cleaned will effect your accuracy. I figured this out the hard way.
The other thing to keep in mind is impact velocity, all monolithic bullets require greater velocity to mushroom then lead bullets. If I remember correctly around 1800fps is the slowest impact velocity Barnes recommends, but faster is always better. When doing load development with a monolithic bullet I will set my effective range based on when the bullet slows to about 2100fps. I set it at 2100fps to have confidence in the bullets performance. With my 300wm, that’s a little over 500 yards and with my 308, it’s about 350 yards.
Hope that makes sense.