You are spot on.

Interestingly, everyone comments that anything over .5 of an inch
(505 Gibbs, 500 Nitro, 500 Jeff) does have alot more effect than
470 et all.

By the way, I genrally prefer Heavy Round Nose bullets over Spire Point
bullets when hunting - from my experience I think they "hit" harder
but in some cases they don't penetrate as far because of the fact they open
up faster. Having done heaps of tests on game when testing bullets
this is just something I noticed.

500 Nitro