I've killed deer with both the 250's and the 300's, all were dead. I prefer the 300 gr lee cast lead with alloy #2 hardness, but thats just me. I'v shot deer with the 250xtp's, (not the magnum) and found they blow up unless you keep the velocity around 1000fps. With the lead cast flat nose bullets 900 to 1200 fps is deadly on deer, putting holes in both sides of the deer with a lot of damage internally. The 300 gr bullets shoot most accurately in my Ruger, but I've been able to get satisfactory accuracy with the 250 gr. Last year (2008) I shot a large doe that was facing me with a 300 gr cast, and upon skinning the deer found the bullet under the skin on the hind quarter, completly thru the the deer entering the chest taking out the heart, lungs, damaging the liver and ending up flattened to a little over 3/4 inch in diameter. I would advise that you choose whatever shoots best in you 454, they'll all kill a deer.