You're assuming too much, John...and the main assumption is that equal energy means equal performance.
I'm not assuming that at all. I'm saying that if you look at a 95gr standard pressure loading for the .38spl and a 95gr .380ACP, they're alike in terms of bullet diameter, bullet weight, bullet velocity, bullet momentum AND bullet energy.
And why restrict the .38 in order to stack the deck in favor of the smaller round?
I'm not trying to stack anything in favor of anything, the question was asked (are they equal), and I'm answering it thoroughly.
In light bullet weight loadings, standard pressure .38spl is equal to the .380ACP, if you extend the comparison to heavier bullets than the .380ACP can handle or to include .38spl +P then they are not equal.
If you're tasked with tearing down a brick wall, would you choose a framing hammer or a 10-pound sledge? While you may be able to swing the framing hammer fast enough to equal the energy of the sledge...or possibly exceed it...it's pretty clear which one will create the most structural damage to the wall per blow.
Well, first of all, the carpenter's hammer has a much shorter handle and that means that the head speed will be much slower than the head speed of a long-handled sledge since head speed is also a factor of handle length, not just the angular velocity of the swing. That means it will have much less speed and mass and therefore much less momentum AND much less energy.
If we assume that the hammers both have about the same handle length, then a person of reasonable strength would be able to swing both hammers with roughly the same head speed. You would expect to get a faster swing with the lighter hammer, but probably not even a 2x improvement. For the heck of it, let's assume a 2x speed advantage for the lighter hammer. Since the head of the sledge weighs at least 10x more than the head of the carpenter's but the swing speed is only 2x slower, the heavier hammer head results in both more momentum (5x more) AND more energy (2.5x more) even though the head velocity is slower for the heavier hammer.
Basically, your problem, as stated, is meaningless because your assumptions don't follow. A typical carpenter's hammer doesn't have more velocity (due to the short handle) and certainly not more energy than a typical long-handled 10lb sledge. The 10lb sledge wins in every category. Even if we try to even things out with similar handle lengths, a long-handled carpenter's hammer still probably won't have more energy because you'd have to be able to swing it more than 3x faster to compensate for a 10x advantage in head mass that the sledge has.
So the reason the sledge is better for the task is because it wins in every category. The reason it seems like a better choice is because it is. It's not because momentum wins over energy because the smaller hammer doesn't have more energy.
If you're facing a charging Grizzly...would you feel better about the potential outcome with a .45-70 firing a solid lead 405 grain bullet...or a .22-250 firing a 60-grain hollow point?
Again, this is a very poor example. If you're implying that the 22-250 has a lot more energy and that's why someone might choose it, you'd be wrong. At only 1386fps, a 405gr .45-70 bullet will have more energy than a 3600fps 60gr bullet out of a 22-250 rifle. Again, the reason the .45-70 looks like the clear choice is that it IS the clear choice. With reasonable modern loadings it wins whether you want to look at bullet weight, bullet size, bullet momentum or bullet energy.
Velocity. Energy. Momentum. All these things are variable, as is the target whenever we shoot for blood. The only constant is bullet mass. The smart/successful gambler never bets on the variable. He puts his money on the sure thing. The constant..
The variances in velocity, energy and momentum from one shot to the next for a given load are trivial. If we're going to talk about trivial differences, then even mass varies somewhat from one bullet to the next since bullets are not all identical.
The only way to assure that the bullet performs the same way every time is to have one that doesn't do anything except penetrate the target. Then, the task is getting it to penetrate far enough to hit something important.
IF you have to choose between reliably sufficient penetration and expansion, then it makes sense to forego even the possibility of expansion in favor of guaranteed penetration. If you can have reliably sufficient penetration WITH expansion, it makes no sense to give up the expansion simply to make the penetration more consistent.
