For example Take a 130 gr 30 cal and same bullet in 180 gr. shoot them at same velocity so they can expand to same diameter and which one will penetrate deeper?
You can have a heavy pancake but it won't penetrate as far as a smaller diameter and lighter weight steel rod. A bullet begins to expand shortly after it hits hair, and how much it expands determines penetration regardless of it's original Sd. In other words bullet construction is far and away the biggest factor in how a bullet performs after it hits a critter. I still think Sd counts for something, and based on my observation remain a fan of bullets that are in the heavyish for caliber class.
I started following my dad elk hunting almost 60 years ago. Between family, friends, myself, and guiding, I've probably witnessed 150+ elk killed with centerfires. and I've chased enough well hit, poor bullet performance elk to form a pretty strong opinion based on experience and post death bullet necropsies.. And yes, I killed a moose and caribou with the X-Bullet on a DIY Alaska hunt 30 years ago--when most folks had yet to hear of Barnes. Plus a couple elk when I got home. I've killed and witnessed elk killed with plenty of TSX's and other mono's like the now defunct Groove Bullets from South Africa (the first monolithic bullet to feature grooves). North Forks (great bullet, but in the end it's more like an expensive Partition), Trophy Bonded, Swift A-Frame etc, etc, are or have been all good bullets and I highly recommend any of the premium bullets (Accubonds are kind've at the bottom of the recommended list though).
The Partition is still my first choice because it performs well across the greatest range of velocities of the bullets I've seen used on elk. Not to mention, sitting in my reloading cabinet are close to 1500 Partition 2nds in a long list of calibers and weights, and all them cost me less than $30 a bag including shipping--some cost me less than $10 a bag.
Everybody can cite examples when plain old cup & cores penetrated well and killed the elk in an instant--I've seen it with me own eyes. I've also seen premium bullets not perform the way I expected. But in the end the premiums are more
consistent in their behavior. Moderate expansion under a range of velocities, deep penetration, is where it's at.
Having said that, my new 308's elk load features the 150g TTSX and I may carry that rifle for my second elk tag this year. I've only seen three elk killed with TTSX's while guiding, but think the bullet did a great job.
As I have mentioned a few times before on these kind of threads, I think in the mid term future lead core bullets will probably be prohibited and we will all be using monos for big game hunting in the West whether we like them or not.
