Ok, something making me wonder about "the numbers".
Just for grins, compare a 77gr 5.56 load with these specs
BC = .42, Muzzle vel = 2700 fps
With this, I am seeing about 420 ft-lbs energy @ 600 yards
Watch this vid, skip to about the 10min mark and watch the impact on the steel plates.
Doesnt seem to have that much "smack" on the plate?
Granted, he is using a Norma USA's 77 grain Sierra Match King, a 16inch barrel and getting around 2468 fps at the muzzle

Now, just for comparison, a 45acp using a run-of-the-mill ball 230 gr fmj round will have around 370-ish ft-lbs of energy at the muzzle.
From experience I know a 45 ball round at 15yds or so, on a plate like that would knock it harder.

Interesting to watch impact effects on steel at different ranges.
here is another vid, using a 20in barrel with a miz of m855 and tracers.
Watch the impact on the steep plates.  Granted these are what look to be cultivator disks, so they are thinner than the typical 3/8 or 1/4 inch ar500 plates.
Note in the comments, he mentions the comparison between a 5.56 @ 600 and a 40 or 45acp

Would be interesting to see some "hot" 77gr loads such as IMI Razor impact on steel @ 600yds.  Anyone care to find/share a range video or target camera footage of various 77gr loads impact on steel at 500/600 yards?

.45 ACP has more momentum, even if the energy is similar. In fact, .45 ACP and 5.56 often have similar momentum at the muzzle.

Neither momentum nor energy are good predictors of terminal performance. 230 gr +P HST at the muzzle has more momentum and less energy than both M193 at the muzzle and M193 at 225 yards. Terminally, it will likely be significantly inferior to the former and significantly superior to the latter.

the BC of the 77gr SMK is .362

Yep, I think youre right.  Not sure where I got that number, I think midwayusa, but that was for the TMK bullet, not the same thing.

BallisticXLR said Metallic Silhouettes circles describe it as Ram-mentum.

What's the technical physics term for more  frontal mass hitting at once then a long pointy thing?



I'm going to make up the phrase " ballistic bouyancy" and start spreading around gun shops

KNOCKDOWN POWUH!

in the first video that's probably also a pretty damn heavy plate that he's shooting at 600 yds. Even in his .308 videos the plate doesn't move very much

Momentum is what helps a projectile break through bones. Energy contributes to depth of penetration.
If "Neither momentum nor energy are good predictors of terminal performance", then what are good predictors?

Meplat?

What matters is both projectiles did not penetrate the plate so both dumped all their energy into that steel and therefore the steel is done for!  The steel might have survived if the bullets had punched a hole clean through and didn't absorb all that energy.  lol

Momentum helps a projectile stay on course, and retain whatever energy it has. Energy is a very deceptive measurement that gets far more attention than it deserves.

No single metric is a good predictor of terminal performance, but the more variables you understand, and the more you understand their interactions, the better you can make an educated prediction of performance by looking at the whole picture.

Why is a good 5.56 bullet extremely more terminally effective than a 230gr 45 acp of any kind if energy isn’t as important as you say it is? It has the same or slightly less momentum than a 45.

Frankly, I don't think there's anything "deceptive" about energy numbers, in general. There's a reason why fpe is listed on boxes of ammo. It's when people start talking about "knock down power" or "energy dumps" that things can get muddled. But that's because the person is confused; not because there's anything wrong with the metric.

Beyond that, regarding momentum, while momentum may help the projectile "stay on course", it's also what provides the ass to to penetrate, break through things, contribute to permanent crush cavity, etc. I'm certainly no expert, but I'd actually like to see more info provided about momentum of various rounds. Another metric / an additional piece of info certainly wouldn't hurt anything. As you alluded to, understanding more variables can be helpful.

Ft lbs of energy is listed for advertising purposes because the layperson thinks energy = terminal performance and demands to know. As for momentum, you can literally compare loadings by multiplying mass by velocity.

I have not found that penetration increases proportionately with energy, even adjusting for frontal area. Momentum was closer but still imperfect. When I asked Doctor Gary Roberts on his thoughts, his response was that he quite frankly disliked engineering calculations, and would prefer that people just shoot the bullet into gel and measure it. I am inclined to agree.

Energy is a poor predictor of performance because 1) it does not account for how the bullet may physically deform and upset and 2) it does not account for energy loss that does not contribute to terminal performance (heat transfer, friction, etc)

Momentum also cannot be taken as a face value measure of penetration, again because it doesn't take into account how a bullet may behave, and also how different objects may behave and resist penetration. If, say, two bullets have differing mass values but the same momentum and frontal area, I would not expect them to perform the same through auto glass, body armor, or, indeed, bone.

I figured the M193 example would be sufficient demonstration, but I suppose a few more examples may be in order...

Hornady 220 +P gr Critical Defense has more energy and certainly more momentum than 147 gr HST. When fired through 4 layer denim, the difference in expansion bordered on negligible and penetration was identical.

147 +P HST improves on both momentum and energy compared to standard pressure, but sees no real increase in performance.

140 gr TAC-XP has far more energy and significantly more momentum than 185 gr +P TAC-XP, with little to show for it.

5.45 7n6 has similar momentum and energy to .223 55 gr FMJ, or M855A1 out of a shorter barrel. Yet 7n6 has been observed to produce little damage beyond crushing effects in flexible tissue, despite penetrating similarly to M855A1.

External ballistics are not good measures of bullet effectiveness in tissue. Again, the better method is to just shoot the thing and look at what it does. In lieu of that, we can look at bullet construction, mass, and velocity independently in order to guess what the projectile will do, but this is no guarantee of performance.

FPNI.

What you're seeing on the steel plate is momentum transfer. Inertia.

Energy really only matters for impact purposes when it's over a certain threshold; when high enough the hydro-static shock can significantly damages soft flesh outside of the immediate wound channel. This is the mechanism by which rifles do rifle-things to targets. Once rifle bullets slow down to pistol velocities, they are typically not better than pistol rounds designed to open-up and function at those velocities. Plus, odds are the pistol round will be more massive than the rifle round and create more penetration. Bullet design and a bullet impacting at velocities within their rated performance thresholds is a bigger predictor of performance than momentum or energy alone.**


**Unless you're talking about 12ga slugs. The just plain fuck everything up.
BIG BULLETS MAKE BIG MOMENTUM

Okay then, so shoot - what??

People who attempt to do their own home-brew-style backyard testing are routinely mocked for their efforts. Whether they're shooting paper plates, or water jugs, or pork butts, or cinder blocks, or whatever else. Or, if they're not mocked, it doesn't really matter anyway because there is pretty much no science and very little consistency employed. And how many people are realistically gonna be able to do actual, scientific, proper gel-testing, on their own, on every round (rifle and/or handgun) that tickles their fancy? The answer is: very few.

Beyond that, since there is "no guarantee of performance" in terms of what a bullet will do with respect to "bullet construction, mass, and velocity", and so on; then to take that argument to the logical conclusion would be to say that people should simply shoot the largest, heaviest, fastest *ball* ammo that they can shoot well (at least in terms of handgun ammo) and not bother with modern ammunition, or pay attention to much of anything else.

Then it would make sense to either search up tests conducted by other people, or infer performance based off of what you know about existing loadings.

"No guarantee" does not preclude me from making an educated guess; without seeing test media performance, I can assume that a thinly jacketed 77 gr OTM traveling at 2700 FPS will probably fragment and penetrate about 12-15 inches, creating a wound channel with a relatively short neck and a large main cavity that eventually tapers down to the size of the recovered projectile. I simply also recognize that there is a possibility of my being incorrect.

Fortunately I don't have to do all that because my preferred 5.56 loading has been validated through gel and game results alike.

throwing water balloons as a kid, if you thew a roughly 1lb one at someone or something, like say, a window, if it busts, then they'd hardly feel it.  water would go everywhere and soak them/it.  but if it didn't burst, it could easily break a window or knock someone around pretty good.

that's effectively what's happening to the steel.  if the bullet holds together (like most 45 would on steel at short range) some energy is used to deform the bullet, and some to heat and sound, but quite a lot goes into moving the plate.    the rifle bullet, however, fragments, and each of the fragments carry significant energy away.   still some sound and heat, but not all that much goes into moving the plate.

if that rifle bullet went into a person though, those fragments would transfer their energy inside, doing substantial damage.   there's a pretty good reason we do tests on gelatin and don't draw terminal ballistic conclusions from steel plates

Time to break out the TKO equation.

How would you compare 230gr +P HST at the muzzle to something like a black hills 5.56mm 77gr TMK at 400 yards? Assuming 2700fps muzzle velocity out of a 16" AR, it'll be traveling at ~1900 fps and producing 626 ft lbs of muzzle energy at that distance. It'll still fragment at 1900, but is probably below the threshold to cause "rifle type" wounding. Would it still outperform the .45 at point blank range? The 77gr TMK would have only 70% of the momentum of the 45 at that point, but around 40% more energy.

Honestly, these things are hard to predict exactly, but if I had to guess:

230 gr +P HST is probably roughly comparable to the lower end of .30 carbine JSP in terms of overall effectiveness in flexible soft tissue, though it produces a differently shaped wound channel (medium size hole of constant width vs greater initial wounding that tapers down).

At 1900 FPS, a 77 gr TMK is traveling at what would be medium speed for a .30 carbine. It doesn't expand as large as most .30 carbine JSP or maintain velocity as well, and definitely doesn't penetrate as much, but it probably compensates for that with fragmentation.

I'd guess on average the TMK would be more effective, though the .45 could be better under select circumstances (e.g. traveling through a limb and/or at a bad angle through a giant dude) since it maintains a constant wound channel and penetrates a bit more. I think they'd be getting rather close though and it'd be difficult to actually determine.

Been wanting to get some 77gr out last 300 but haven’t had a chance. Would be a nice poke!