Ash,
A reason or two for using the 450 grain bullets in the 45-90 :
1. Great past success with 400 and 450 grain Punch, North Fork and Kodiak bullets in 45-70 and 45-90.

2. The 45-90 has 96% the case capacity of the .450 Win Mag, a caliber thought by many to have too little capacity for 500 grain bullets.

3. Experience taking Nilgai, water buffalo, Cape Buffalo, and large exotics with 45-70 with bullet velocity less than 2000 fps.

4. Last, but VERY meaningful; 50 yard shot with 45-70 430 grain Punch (brass bullet with lead filled base) at less than 2000 fps shot/punched through 5/8 steel swinging target plate! A clean, daylight hole! Same bullet just whistles through cape buff broadside shots too!

Please forgive my repetition, but the bullet does the killing!

For those that do respect the modern .45-70, imagine how few animals would be left in Africa if the modern .45-70 rifles and ammo were available to the African citizen population?