BBTI - Muzzle Energy

[smokehouse4444]

When I was a kid, I loved pouring through every chart and stat sheet I could find with muzzle velocities and muzzle energies. Especially ME's. I came to realize over time that they didn't mean all that much...more of a guide if you will since there are so many variables. After a recent thread I was turned on to the BBTI site. Of course, I had to just sit there for hours looking through all of the numbers, and it seems the numbers ring somewhat true for me. Taking the higher "clump" of ME numbers for several common calibers, it looked in this order:

380 150-200 (3")

38 Sp 180-240 (3")
250-340 (4.5)

9mm 340-400 (3")
420-460 (4.5)

40 420-520 (4.5)

45 480-540 (4.5)

10mm 520-600 (4.5)

357Mag 400-450 (3")
640-680 (4.5)

41Mag 630-800 (4.5)

44Mag 800-920 (4.5)


Seemed kind of "right" to me as far as the pecking order. (Not trying to start any wars here)

I also found it curious that the 9mm Speer Gold Dot 124gr that everyone loves so much (and I recently bought a box) isn't nearly as potent as the Corbon 115gr JHP+P, so why do so many buy it instead? Price? Again, not trying to start a war, just a casual observation, and question.

 

[tipoc]

It's not clear to me what the figures you show mean. For example you show...

9mm 340-400 (3")
420-460 (4.5)

Ok I can see something is a 9mm beyond that I can only guess.
Do you mean that one round has 340 ft.pds. of energy at the muzzle and another has 400 ft. pds. of energy at the muzzle? What rounds? What is the 3"?

I don't understand what you have written. That's all.

tipoc

 

[Mike Irwin]

Ultimately, muzzle energy is really not a particularly good indicator of a bullet's ability to stop an attacker.

Bullet expansion, combined with penetration, are far better indicators of performance.

I'll take a bullet design that consistently expands well and penetrates deeply, but which doesn't have as much muzzle energy, over one that has lots of ME, but doesn't show good expansion and/or penetration.

 

[DanThaMan1776]

The projectiles "energy" really only starts to matter, from a defensive standpoint, I'm the much higher velocities (CF rifles). At velocities around 2200 fps and up, the "hydrostatic shock," or what is observed by the temporary cavity, plays a roll in terminal performance. A 40gr 22 lr going at roughly 1100 fps pokes a hole and is suitable for vermin... Throw on 15 grs and 2000 fps(which is the more significant dif?) and you have the 556, suitable for a lot more than the 22 lr.

With pistols, you need to factor in penetration before anything. Good expansion can and should be sought in the modern day (given how reliable the bullet mfc technology is) but I'd worry less about energy.

 

[BlueTrain]

I agree. I'm waiting for the .32 Long to come out with a Silvertip bullet. If you can get it in .32 ACP, I see no reason it shouldn't be available in .32 Long.

 

[Mike Irwin]

"At velocities around 2200 fps and up, the "hydrostatic shock," or what is observed by the temporary cavity, plays a roll in terminal performance."

At roughly that velocity threshold, the line between temporary cavity and wound channel begins to blur because the energy imparted by the velocity begins to do damage all its own, as evidenced by tearing and other kinds of damage to tissues not affected by the permanent wound channel.

But that's rifle velocities, which are difficult, if not impossible, to achieve in a handgun, at least most handguns suitable for defensive/carry purposes.

 

[Hal]

I also found it curious that the 9mm Speer Gold Dot 124gr that everyone loves so much (and I recently bought a box) isn't nearly as potent as the Corbon 115gr JHP+P, so why do so many buy it instead?

Muzzle energy is figured as weight times velocity.
If you double the weight of a bullet, you double it's energy.
If you double the velocity, instead of doubling the energy, it quadruples it.

In the black powder eara, velocities were pretty fixed.
In the pre-minne ball era, bullet (actually round balls) weights were fixed - by the diameter of the bore.
If you wanted a heavier slug, you went to a larger diameter ( caliber).

(Still with me? -1)

Ok - so, having that information,,,,the 115 gr. (lighter slug) is moving faster.
The diameter is the same (.355 in.").
So - yes the faster Cor Bon bullet will have higher ME figures and appear "more potent".

Muzzle Energy is really a critical piece of the puzzle,,,,but,,,not in and of itself & certaily not from any foolish notion of "energy trasfer" or "stopping power".
Downrange, when a bullet hit's it's target, it takes energy to make the bullet expand.
(still with me? -2)

This is where things get fuzzy...
You need to understand the importance of cross sectional density - or sectional density as it's ofen referred to - or SD for short.
SD is the relationship between the mass of the bullet and it's diameter.
Once conical bullets came into use, it was possible to increase the weight of a bullet and still maintain a smaller diameter.
The greater the weight (mass) the better the ability to penetrate.

When a bullet expands - 9mm/.355" or .35 caliber for illustrative purposes - expands it's frontal area to a larger diameter, .50 cal or .60 cal., it changes the SD figures - due to the bullet now being - for all intents and purposes - a larger diameter.
(still with me? -3)

As the expansion takes place and the bullets ability to penetrate decreases, more available energy will aid in that process - remember it still takes energy for the bullet to expand.
Expansion - just for the sake of expansion is counterproductive since the incresed SD is decreasing the ability of the bullet to penetrate.
A worst case scenerio is that expansion all takes place on impact and nealr all the energy the round has goes into making the bullet expand.
For example - If I were to take a 115 gr. .357 bullet and load it to ~ 2000 fps out of my Marlin Cowboy II and fire it at a block of gel, it would probably expend close to 100% of it's energy on impact and literlly shatter (explode).
(still with me? -4)

What you really want is controlled expansion.
The bullet should hit and enter the target, penetrate a few inches, then begin to expand. It should expand at a rate that comes as close as possible to reaching it's maximum diameter as nearly as possible to any internal vital organs, then stop just short of exiting or just barely exiting and falling a couple of feet behind the target.
(still with me? -5)

The reason the 124 gr Gold Dot is well regarded is that, despite having a lower muzzle energy, it has slightly greater mass (124 gr vs 115 gr).
With a greater mass it has a slightly better SD.
With a slightly better SD, it will have slightly better initial penetration.
Once it's journy through the target continues, it has a very good rate of expansion as it penetrates to the vitals.
(still with me? - 6)

Bottom line is that the others above have it right.
ME isn't something to be concerned with for a defensive situation using a good brand of factory ammo loaded for defensive purposes.
The ammo manufacturers do testing to determine the optimal rate of expansion at the optimal velocity - then determine how wide that velocity band can be.
The mentioned 124 Gold Dot just happens to have a lower optimal velocity - which in turn delivers a lower ME - which on the surface make it appear "less potent".
(did I lose you anywhere?)

 

[jmortimer]

People who like hard cast bullets with large meplats know that a big "slow" bullet will do just about anything. For example, a 255 grain hard cast SWC at 950 fps will shoot through just about any animal on a broadside. It will shoot through a few feet of ballistic gelatin. It will make a fairly large hole. It will do just about anything a handgun can do. At 511 ft lbs it seems fairly tame compared to a .223 at 1,300 ft lbs but it can do far more than a .223 which would be a compromise with a non-expanding FMJ or an expanding bullet. Against light targets the .223 will do a real good job, but not so much as you move up the food chain where the .45 Colt will still work well. The "No Expansion" large meplat bullets work real good.

 

[tipoc]

Hal gave a good summary and what jmortimer sed is true as well.

Energy figures are particularly useful in rifle rounds as a part of what you look at when it comes to bullet and caliber selection.

For example if you know you are after sheep in mountainous terrain and the shot will likely be a long one you want to select a round that at 200-300 yards will have the power to deliver a killing shot once it reaches the target.

A 30/30 would be a fine choice at up to 150 yards or so. At 300 yards the 30/30 with a 150 gr. Remington Core-Lokt bullet has about 565 ft. pds of energy at it's disposal. As much as the 45 Colt discussed above at the muzzle. But a long shot for a lever gun with this round at this distance the trajectory tends to curve

A 7mm Remington Magnum would be a better choice at 300 yards. With the same brand and type bullet as mentioned above we get 1792 ft. pounds of energy at 300 yards. The round will shoot flatter than the 30/30 at that distance and deliver more than three times the punch with a bullet of the same weight.

In either case you are looking at light weight rifles with little recoil which may assist in accurate shooting.

Planning to hunt with handguns? Energy figures at longer distances are one factor to look at.

This is one way in which energy figures are useful.

tipoc

 

[micromontenegro]

Muzzle energy is figured as weight times velocity squared

There you go

 

[smokehouse4444]

Thanks so much for the great replies guys. I had long ago kind of disregarded ME as a real indicator of power for rounds, knowing that the velocity was a much bigger part of the equation. The 45 acp suffers some from that as it is so much more of a slow moving projectile. Your very in depth explanations were great...and no, I wasn't lost anywhere. I just noticed that the muzzle energies did seem to follow the normal steps of power from the different ammo.

By the way, the (3") and (4.5") is simply barrel lengths. I used 3" and 4.5" simply because they are handguns barrel lengths that I own, and are fairly common. Much appreciated guys.

 

[Hal]

Muzzle energy is figured as weight times velocity squared

Thanks - I always mess that up!

 

[tipoc]

Keep in mind that one foot pound of kinetic energy is the amount of energy used to lift a one pound weight one foot above the ground at a certain point on the earths surface. A ft. pd. of energy is a measurement of kinetic energy. It is a measurement of how much energy is available to perform a certain task. Or how much work the bullet can do.

It does not tell you how hard a bullet strikes or how deadly it is or how much "shock effect" it has. It is an indicator of how much work the bullet can perform or how much ability to do work is available to it. As said earlier energy is expended in bucking the wind, in noise, in penetrating the target, in expanding, in heat transfer, etc.

So as folks have said it is one factor to take into consideration. But it's not meaningless. More important in long guns than short.

tipoc