I'm starting to get my plans together for a cape buffalo hunt in a couple of years. I'm torn between the 400 and 420 gr .475" cast gas checked bullets (both in the long flat nose configuration). On the Beartooth site "calculator" there seems to be a compromise where the lighter bullet might actually give slightly (10%) better penetration due to the ability for marginally higher velocity to help offset the lighter weight. Where as energy (1/2MxV^2) isn't completely relevant in my mind due to there not being any expansion, momentum (MxV) on the other hand would be due to better penetration. Using rough numbers from reloading manuals, again the 400 gr. seem to have an advantage.

I realize that all of this is theoretical but at this point I have nothing else to go on, but some of you might have in-the-field experience.

That would be my choice of the two in the 480. Weight is great, but you also need some velocity for good penetration. How much of a speed kill does 20 grains more bullet beget according to your data?

I'm am quite fond of good hard cast bullets, but went an alternative route for my Argentinian water buffalo (the original plan was Africa but my PH suffered a stroke months before the trip was supposed to happen). Anyhow, I used CEB's (Cutting Edge Bullets) 340 grain flat-nosed copper solids in my .480 for that hunt. They are lighter in weight as there is no lead core, but they are easily as long as a 420 grain bullet. These bullets over a dose of Power Pistol gave me an accurate and lethal load. The bullets are a bit spendy, but your trophy fee will be a lot more, and bullets are an area where I don't think a person should cut cost.

Rick, Another way to go (but expensive) is Grizzly`s loaded 480 Ruger Punch bullet load. They have caught up with production and I can tell you the penetration will be all you can want. I have heard of some accuracy issues but never experienced them my self. Don`t know right now if you can buy the bullets alone for reloading. However, no matter what bullet you choose I wish you good luck....
PS- The buff can be kinda big and a handgunner needs all the penetration he can find..

I bought some Punch bullets not too long ago-380 gr. .475. Testing them now on groundhogs. Accuracy is excellent. Penetration is great!?!

Doc, Are you getting complete penetration?

Id echo above. The ceb bullets are great.

Yes, KRal, complete penetration on groundhogs!! Also on a water buffalo years ago, but with 425 gr. Cast Performance. Big boys, bigger than Capes.