Re: Brush bucking...
I've read about numerous tests, and done my own testing and thinking, and have concluded:
1) The high velocity light bullet will deflect the most (and loose the most energy) because the hydro static shock of hitting a wet branch is magnified by velocity. Test done with dry kiln dried wood do not accurately reflect hitting a sap filled branch or sapling.
2) The harder a bullet is, the better it will penetrate brush. Furthermore, premium bullets that produce a uniform mushroom (as opposed to softer bullets with a slanted mushroom) are more likely to stay on target. Factory 130 gr 270s will deflect wildly even on very small brush. I fired 3 shots at a deer I had dead to rights and never touched it. Went back the next day and saw were the bullets hit tiny branches that did not show up in my scope, and then found where they had deflected and hit trees. They deflected far worse than I would have ever imagined. Subsequent ballistic testing showed those bullets were soft and developed a slanted mushroom, even in uniform test media.
3) Since 243, 270 and 30-06 all generally have a 1 in 10 twist, the 30 cal will have far more gyroscopic stability based on the increased diameter. If you understand how a gyroscope works, it just makes sense.
4) If you have to penetrate brush, you better have a lot more than the minimum amount of energy needed to harvest your game. IMO, this is where the 30-30 comes up short as being a good brush gun (it is a good, handy, close range gun).
I have found the 30 calibers (06 + 300 Win Mag) loaded with premium bullets (the 300 slightly down loaded or the 06 loaded hot) to be far more effective than the 270 or 270 Win Short Mag similarly loaded (in brushy conditions, for clear shots they are wonderful).
FYI, Full Metal Jacket bullets (even from a 223) do well in bucking brush. But with expanding bullets they do not go straight, and do not have the retained energy to effectively take big game.