gopherfan
For deer I am a 240/250/260 fan and for elk I use 300 grain projectiles. I believe the difference in construction of the two bullets is the reason.... the 300 is normally a stronger bullet with thicker copper on the bullet - a perfect bullet for thick skinned animals such as elk, moose, or bear. Two years ago I shot a really nice whitetail buck during elk season, so I was loaded up with a .458 Nosler 300 grain partition. I shot the deer at a ridiculously close range of about 15 yards.... the 300 entered and passed through so quickly it really did not get chance to do much other than make a hole - expansion had barely started as it passed throught the hide on the other side.
The opposit is true when using the 250 speer or 260 Nosler - the bullet copper is not as strong and the HP is deeper in both bullets and expansion and Hydrostatic shock begins as soon as the bullet passes through the hide on the close side. The bullet still passes through the deer but it creates a great deal of shock to the animal. The little toehead I shot this year with the 260 Nosler also shows me how effective this bullet or even the speer is out to 170 yards.
Just my thoughts... Chapman Gleason went the other way this year with a deer he shot... he used a 300 grain Speer Goldand it performed very well for him...
If you believe Hornady advertising - more deer have been killed with a hornady 240 grain XTP than any other bullet...