Ok, Drilling, he said FRONTAL AREA, not diameter!!!! Frontal area---assuming we're talking wadcutter bullets with perfectly blunt noses, and not the spitzers typical to the .270:

Area of a circle (the end of the cylindrical bullet--i.e. frontal area of the bullet)=PI*R^2, so for a .270win that's (.277"/2)^2*3.141592654, which equals 0.060 square inches For a .45-70 using a .458" slug, the frontal area is (.458/2)^2*3.141592654, which equals 0.165 square inchest of bullet face. By my calculations, that's 2.73 times the facia area of the .270's bullet.

Of course, that can cut both ways, yes, it effects a much greater area of tissue and gives a bigger "smack" upon impact, and the fact that it uses an extremely blunt bullet compared to the .270's spitzers, the "smack" will be even greater, but then again, say I've got 1000ft.lbs. of energy behind either bullet, the force per square inch is going to be only about 1/3 in the .45-70 than in the .270...which isn't necessarily an unfair analysis, since many of the .270 and .45-70 factory loadings available are fairly similarly powered in muzzle energy.

But then again, the .450 and .45-70 have about 2.5x the bullet MASS as well, so when it's big face runs into something, it'd really like to keep on going...

I've hunted elk with a .450 (and also a .45-70 among half a dozen other cartridges), it's certainly a good choice. It is a heavy bullet, so you've got to practice a lot to really get to "know the rainbow", a .270 that's dead on at 100yrds might be 1" high at 50yrds and 2" low at 200yrds, but a .450M dead on at 100 might be 4" high at 50 and 10" low at 200, and somewhere between there for ranges between... You don't take a heavy bullet straight walled cartridge afield without knowing where it hits at different ranges, not just looking at a chart, but actually shooting and seeing where your gun prints for given ranges you might take a shot at.