The Big D: Temporary or stretch cavity, is really not an issue except in two cases. The first is if you hit an internal structure which is not made of highly elastic tissue (the liver or kidneys for example), the second is when the temporary cavity is of a size to be larger than limit of tissue elasticity of the area of the body hit. The second only really applies to limbs if you're shooting something smaller then a .50 BMG (even a .338 laupua doesn't generate nearly a large enough temporary cavity to cause an issue in the torso).
The Alaskan:
I suspect 30 cal shooters don't discuss "fragmentation, expansion, yaw" etc because it's not terribly relevant. You said you're looking at buying an M1A.
Fragmentation, expansion, and yaw are the three ways a bullet can increase the permanent wound cavity which is the only way to cause injury. A .30 cal shooter who doesn't discuss these isn't doing their homework.
The main reason fro the 30 cal popularity is straight out penetration. 30-06 ball ammo will blow through a lot more cover than those AR15 pop guns. (Comparatively speaking, of course.) Add to that, you get the ability to effectively hit target out past the AR15's maximum effective range of 550 meters. At least that's the number they made me memorize in the Army.) Trouble is, you pretty much never get an opportunity to use that long range in battle-historically speaking.
If it was just penetration, then why not issue AP rounds all the time? M995 (5.56 AP) will do a dandy job of punching holes through things .30 cal M80 ball might have issues with. I certainly agree that a .30-06 black tip AP round will certainly outperform M995 in penetration, but a .30 call pencil hole is nothing special ballistically (it's basically a narrower wound cavity then a .38 spl hard cast wadcutter). I'll give you the distance argument, but in WW2-Vietnam, the engagement range really never moved out into the distances where 500 meters was doable too often.
I know that if I hit someone with a 30 cal bullet, he's going down. You can talk about terminal ballistics all you want, and, most assuredly, those remarks have some validity, but the 30-06 ball bullet served this country well for half a century and through two world wars and a smaller war (Korea). There are literally MILLIONS of dead soldiers lying in battlefield graves all over the globe that will attest to the 30 cal's efficacy. It's kind of hard to argue with that kind of success-with or without a slide rule.
Okay this is exactly what I'm talking about. Yes I know the .30 cal M2 ball round has put a lot of people in the ground. So have a lot of other calibers. Why does the .30 cal round (in whatever flavor, .30-06, .308 etc.) have this reputation and following is my question? What makes it so dang effective? As I mentioned earlier in this post, there are three things a bullet can do to increase its permanent wound cavity. .30 cal M2 ball really doesn't do any of them, so WHY is it effective? Again, it really makes a wound track about equivalent of a .38 wad cutter, so why is one considered the hammer of righteousness and the other a really good way to get yourself killed in a gunfight?
Daisycutter:
Diameter is only one dimension. Multiply the difference by 3.14 or π to get a better perspective in terms of circumference... Or square the radius and then multiply by 3.14 for the area. The difference grows dramatically, and you're only still in the 2-dimensional world. You gotta multiply by the cube (^3) before you get a real appreciation why it would feel different in the real world.
See post #11 for the math already done in 2 dimensions, the overall volume of the round really doesn't matter as it's basically cutting a channel based on it's exterior dimensions. I will say that volume and mass do effect penetration depth.
The 30 caliber is substantially larger, generally carries about double the energy, and causes far greater damage based upon a long history of empirical data.
Not to mention one of Newton's Laws regarding an equal and opposite reaction. The recoil difference between a 30-06 and a 223 should be a clear indicator of each projectile's felt "effectivity" on the receiving end.
So the effectiveness of the round is based on KE then? Even if a through and through wound (a very common occurrence with M2 and M80 ball) doesn't really have much energy deposition?
I'm not arguing with anyone that the .30 bullet has a well proven track record of effectiveness. I just want to know WHY. If you test M2 or M80 ball, it's really nothing special in terms of terminal ballistics. Is its reputation just built on it's track record, from when nothing else was available or is there actually something to this round that's generally not noticed or discussed?
-Jenrick