Some pretty ugly stuff.
Lately, I've standardized my inventory of bullets, which in turn has resulted in my using the same bullets in different cartridges (implied: different velocities). Over the years, I've drifted toward Hornady almost exclusively. However, many of the guys I hunt with are shooting fusions, BTs, etc. I'm coming to be a believer in the following:
1. Most of my hunting (and friends') is done with "standard" calibers, with game encountered no farther than 300 yards. I haven't completed any analysis yet, but the results of the past ten years or so tend to indicate that factory (CoreLokts) and non-premium bullets (Interlocks) I'm using perform best when muzzle velocity starts somewhere in the 2700-2900 fps range and when the game is from 100-300 yards away. When the game is inside or beyond those ranges, bullet expansion begins to fall off. On the other hand, some of the guys I hunt with who've used premium bullets seem to have issues with expansion on anything under 200 yards. We haven't collected anything outside of 300 yards that I remember in order to compare, but it's become somewhat apparent that bullets have an "expansion sweet spot" which is influenced by bullet construction (standard -vs- premium) and impact velocity, which is range dependent.
Were we to drive those bullets faster, to the point that the impact velocity (for sake of suggestion, let's just say it's 2000-2200 fps) is achieved at 400 yards or beyond, would those bullets perform the same way they do at standard velocities? I can't answer that, but it's a tempting analysis to do on a Sunday afternoon if the wind picks up again.
2. From somewhere in my youth is a story about a nonresident hunter (probably a Texan, since I lived in SW Colorado at the time?!) who came to hunt elk but had lightweight "varmint" bullets that ended up blowing up on the elk's shoulder without penetrating. That's stuck with me to the point that I never use a varmint bullet on big game (duh), and since my experience with match bullets has been that most have more similarity in construction with varmint bullets than with true hunting bullets, I won't use a target bullet on big game either. The Bergers, SMKs, and A-Maxes work great on the KD, but the reports I read and hear about the Berger Hunting or the other match bullets used on game have typically been pretty dismal. This thread suggests that as well.
An interesting discussion possibility here. My suggestions then would be that bullets, depending on their construction, expand best within a window of impact velocities. That window can be moved in closer or extended by decreasing or increasing muzzle velocities, respectively. I'm not including pistol-calibers here, that's a topic for a different Sunday afternoon. Also, that even when marketed as such, lightly-jacketed match bullets really aren't as suitable for hunting big game as are bullets constructed with heavier jackets?