Back in "Teddy's" time they didn't know you could hand load the 405 Win w/ a 400 gr. bullet to close to 2,000 fps which is really close to the .450/.400 three inch cartridge. Brittany Boddington used this load to take Water Buff in Australia in 2004 and Cape Buff in Africa in 2006 . This load should be fine for bear. Advances in powder and bullets have come a long ways since TR hunted Africa many moons ago. When you load the 405 Win. w/ 50.5 gr. of H4895 and an OAL to 3.230 w/ a 400 gr. bullet you have serious power that will handle anything that walks. If you load this round w/ 53.5 gr. of Ramshot TAC you will push the 400 gr. bullet a little over 2,000 fps. Yea a 400 gr. bullet at 2,000 fps, might just do the job.