Probably. All I do is neck up from .223 to .284 so the brass will fit and all you would have to do is make sure the bullets are seated deep enough. A 120 gr 7mm bullet really isn't very long so you shouldn't have any issues. The good thing about using .284 vice .277 is a lot better selection of bullets but other than that there probably isn't any major difference.

The 7mm TCU has proven to me to be very effective on southern whitetails but I admit I haven't tried it on anything bigger. The 120 gr Nosler BT is inherently accurate and tips deer over very nicely. On days when I don't feel like lugging a long gun around I grab the Contender and know that if I miss a deer at 100 yds it will be my fault and not the fault of the rig.