JESUS CHRIST!!! WTF do you need a 180 gr. bullet to shoot a whitetail??? Most .30 caliber rifles (including the .308 and 30/06) have a 1/10 rate of twist, sometimes 1/12 but usually 1/10... 1/10 .30 calibers usually shoot best with bullet weights between 160-170 grains. 150 grains might be a little unstable at greater ranges but I doubt enough for you to notice. Whitetails don't take a lot of killing; an 80/90 grain 6mm bullet (like a .243) will kill a whitetail like chained lightning provided you do your job. And on the opposite spectrum a good friend of mine feels it necessary to fire a .338 Winchester Magnum with either a 200 or 225 grain bullet at them and has had one run nearly a mile completely exanguanated and with internals turned to jelly... I believe a bullet in the 120 to 140 grain range to be excellent whitetail ammo; I've been hunting with a 7mm using a 120gr. ballistic tip and it will drop them in their tracks. When I was hunting with a .308 I liked the 150 ballistic tips, I handloaded but you can buy similar ammunition in this caliber and 30/06. It's a fairly light bullet for .30's and doesn't kick all that bad. Slightly heavier loads in the 160/165 range are also not too bad and may be a little better for long range shooting. I don't really like hearing about people shooting at deer at 250+ yards because as a realist I know most people THINK they shoot well enough to do that but DON'T... I hate the idea of wounded animals, that bothers me. But, I've taken some whitetails at stupid ranges so I'm not going to say don't do it. If you and your equipment are up to long shots then take them. As for "brush guns" there's really no such thing. I know a lot of people espouse big heavy bullets for hunting short ranges in thick woods but if you have to shoot through a thicket to hit a deer you don't need to shoot at it. An 1/8" twig will deflect a 647 gr. 50 BMG bullet enough to miss its target, much less a 200 grain bullet moving 2/3 as fast. Just use the same ammo you hunt with in the longer ranges and don't shoot through crap.

125 gr. in a typical .30 is too light... Not because it won't kill a whitetail (it will, quite easily as a matter of fact) but because of the typically rifling in .30's... Remember either 1/12 or 1/10 with 1/10 being the most common. The bearing surface on lighter bullets is much shorter and they need to be spun slower than heavier bullets... Typically rifles that shoot bullets in this weight have slower rates of twist; usually 1/14. A 125 gr. bullet fired out of a 1/10 twist bbl. will not be nearly as accurate or stable as a 150-165 gr. bullet. They have a greater tendency to yaw and tumble. Case in point that some of you military types may have experience with. The original 5.56 load is the M193 which is a 55 gr. bullet; the original M16's used 1/12 bbl's. In the mid-80s NATO standardized the Belgian SS109 bullet which is 63 grains. The bullet is about .100" longer than the M193 and required a faster rate of twist at 1/7. But, if you shoot a 55 gr. out of that 1/7 twist bbl. it will keyhole the target (if you hit it at all) at 50 yards! Same thing if you shoot a 63 gr. SS109 out of a 1/12 bbl... Most of the commercial AR15's now use a 1/9 twist bbl. for a "best of both worlds compromise;" you can shoot either 55 or 63 grain bullets equally as well. The military still uses the 1/7 twist primarily because they are only shooting the SS109 ammunition.

Now, to a physics lesson: Which one is a better sniper rifle, a 5.56 or 7.62? Let's put this into context: the 5.56 has a 63 grain bullet with a muzzle velocity of 3300 fps while the 7.62 has a 173 gr. (Lake City Match) bullet leaving the muzzle at 2650... Which one shoots farther and flatter? You might say the 5.56... You'd be wrong... Why don't we see .22 caliber (that's 5.56mm) 1000 yd. match rifles? Because lighter bullets are affected much more by gravitational pull and by windage than heavier bullets. They may start out faster (considerably) than the heavier .30 bullet but they lose their kinetic energy MUCH faster. Heavier bullets retain their energy longer because they are affected by Newton's Laws LESS so than lighter bullets. Light and fast is good...To a point... But it's at that point that the heavier bullet takes over and retains not only its velocity but it's energy for a longer period (ie., range) than a lighter/faster bullet. Plus, when you whack someone (or something) with a .30 bullet they typically don't get up...Unless you hit something very vital at extended range with a .22 they may shoot back at you (or not be on your menu).

I still maintain that the BEST loads for whitetail deer in .30 is a bullet weight between 150-165 grains...

You want the LIGHTEST bullet that will do the job on a whitetail... Typically the heavier rifle loadings 180 grain-up will overpenetrate and not dump all of their energy in the body cavity therefore you've wasted energy. Personally the ideal whitetail bullet is between 120-140 grains and expands RAPIDLY. Most 200-220's in .30 and .325" calibers are designed for game animals that are much larger and have much thicker vital areas. They're designed to begin expansion 8"-10" inside the body cavity; well, on a typical whitetail you're just about in the middle of the heart/lungs before ANY expansion takes place. Combine that with the kinetic energy of that heavy bullet and they typically sail out the other side leaving a large hole. But, in the heart and lungs you have a much smaller hole. On my deer pistol (that's right dammit, a pistol) I shoot a 120 grain Nosler ballistic tip in 7mm... It will begin RAPIDLY expanding about 4"-6" inside the body cavity and by the time it reaches the heart/lungs (truthfully this is rare since I try to shoot most of them in the neck) it's fully expanded and liquifies everything inside. Usually the remains of the bullet can be found just under the skin on the opposite shoulder; thus dumping ALL of its energy inside the body cavity and causing the maximum wound channel.

Don't try and associate rifles and handguns the same way, however. You're dealing with MUCH greater velocities with rifles. A big heavy handgun bullet moving at a moderate velocity typically imparts much more energy than a light, fast handgun bullet... With rifles almost the opposite is true; big heavy bullets travelling at a pretty good clip will always overpenetrate when fired at light-skinned game like whitetails (and humans) where a lighter bullet that is designed for these lighter skinned/bodied animals will be much more devastating due to their rapid expansion and dumping of energy without over-penetrating. However, try shooting an elk with a 120 grain bullet intended for smaller game and you'll quickly figure out that the rapid expansion does not penetrate deeply enough in its heavy body to be affective. But a 180 grain to 220 grain bullet will penetrate AND expand.

Edit: This might be confusing to some as it sounds like I'm contradicting myself in the earlier statement regarding 5.56 vs. 7.62: keep in mind that in this instance I'm referring to NON-EXPANDING FMJ ammuntion that is MANDATED by the Geneva Convention for military use. A .30 hole is always preferable to a .22 hole when no expansion is available... You know...The bigger hole principle!