I have a Glock 21. It is a .45. The manual tells me that I can expect the muzzle energy of this gun to be approximately 460 J. (That’s joules, right?) By way of comparison, their 10mm, a gun which I was told was too powerful for the FBI agents causing them to switch to a .40 cal., offers an approximate 750 J.
Now, I’m looking at a manual for a Taurus revolver. Specifically, the .357 magnum is listed as having a bullet weight of 158 grain (a typical defense load, I’m told) and a muzzle velocity of 1450 feet/sec (why do they call it muzzle velocity when fps doesn’t include a direction? It’s not a vector dammit!!). So I go to Rob’s reloading pages and plug these in to get a muzzle energy of 1000 J! (That’s 1000 J, not 1000 J factorial.)
Is this reasonable? Has the .357 really got more than twice the muzzle energy of a .45 ACP and at least one-quarter more muzzle energy than the 10mm?!
Bullet muzzle energies are one of those things where there is a wide range of values that are possible, depending on the loading, bullet weight, firearm, and testing conditions and error. Plus, I’ve found that people often mix and match Joules with ft-lbf on charts and comparisons.
This calculator here shows the following energies.
First off, “grain” is not the unit of weight used to measure the bullet, but rather it’s the unit of measurement for the gunpowder charge inside the cartridge that fires the bullet.
So, it’s a simple equasion: Weight of bullet + Powder charge - varibles of energy loss in the form of things like the pistol’s blowback mechanism, the gap between the cylander and compression cone (in revolvers) and resistance from rifling and barrel length = Muzzle velocity. Since you haven’t stated the grain behind the .45, it’s hard to say, but in my experience that’s not unrealistic – .357’s are very high velocity because of the low weight bullet and high grain mix.
While a .45’s bullet weight is pretty high (around 230 grain), it’s pretty slow (around 850 ft/s). That only works out to about 500 J.
The .357 is a magnum cartridge, which means quite a bit of powder is used to propel the bullet down the barrel (as compared to the bullet’s weight). Because of this, the .357 bullet is pretty fast – around 1500 ft/s. And since energy is proportional to v[sup]2[/sup], the .357 has quite a bit more energy than the .45.
But energy isn’t everything. Size also matters. Whether or not the .357 is more effective than the .45 is a matter of debate. Personally, I think penetration (and thus bullet speed) is more important than bullet diameter.
For most of us shooters/reloaders the velocity is measured in Feet per second= fps the 1st measure is at muzzle. Lets take a .357 Magnum load with a 158 Grain Gr jacketed bullet Powder = Unique at 8.0 grains
Muzzle velocity = 1200 fps energy = 505 foot pounds ft. lbs.
at 25 Meters V = 1054 fps E = 454 ft. lbs.
at 50 Meters V= 1085 fps E= 413 ft. lbs.
These are test conditions depending on Gun= rifling twist rate/ barrel length/ primer/ case/ just about everything imaginable. with powder/ barrel length being high on the list. Powders are classified by burn rates and handgun powders are very fast burning powders. for proper performance the powder must burn completely before the bullet leaves the barrel. if its too fast and burns up before the bullet leaves the barrel, the bullet will start decelerating.
Reloading is a science, and not for everyone.
Hope this clears up some of your questions.
The 10 mm has a Muzzle(M) velocity(V) of 1030 fps & M Energy of 425 ft lbs
The 40 s&w " " 990 " 390
the .357 Mag " " 1240 " 535
No the 357 doesn’t have twice the energy of the 10mm all these loads can have a different bullet, and comparing them are sometimes hard. The problem with the 10mm was recoil. The gun was hard to shoot in a small frame concealed carry gun. the 40 s7w is just a 10mm short if you will.
Bullet weight is sometimes measured in grams but usually in grains. example= 180 grains = 11.66 grams. Joules is very rare, maybe in a forensics lab.
My choice for a S&W 1006 over the .40 was simple-the .40 had a fatter grip, owing to the stagger clip design-the 10mm is inline and allows multiple concealed carry positions not afforded by the .40 weapon.
As far as the 10 being a hard to shoot weapon, that’s hogwash IMHO. I’ve gone to the range and after 3 or 4 bricks find it no different than if I’m using any other weapon.
I have tested it out with a few problems from this posting (as well as others) and it seems to be error-free. Then again, it is now 3:00 a.m. and I’m not at my sharpest mental capacity.
If nothing else, I caught an error in a posting by gbrohman -
a 158 grain bullet at 25 Meters; Vel = 1054 fps Energy = 454 ft. lbs
there’s something there that’s poted incorrectly.
Notice that at 50 meters, the bullet has sped up to 1085 fps.
One thing to bear in mind is that recoil is proportional to momentum, which is bullet mass x bullet velocity (I’m going to ignore propellant gas mass and velocity, although that isn’t strictly valid.)
Muzzle energy on the other hand is half bullet mass x bullet velocity squared.
So if you double the bullet velocity and half the bullet mass, the recoil stays the same but the muzzle energy doubles. Of course, this means you need more powder in the shell, the barrel pressure increases etc. so there are practical limits. But a tiny bullet that screams out the barrel can have a lot of energy.
matt
You are quite correct about calculating recoil and muzzle energy. That is why a cartridge such as the .223 has great muzzle energy (and velocity) with minimal recoil. gbrohman
And because of writing that calculator I discovered that error. (At first I thought it was my calculator). But that’s okay. No reason to apologize.
Okay, so equal & opposite actions has to do with the momentum and not the energy; i.e. momentum going that way equals the momentum coming this way, hence the kick is bmbv and not (1/2)bmbv^2. Right? Cool, thanks.
Yeah, but people will claim anything to make a sale. My error:
I looked at the manual online again and those numbers are the limits that the guns are manufactured to withstand, not the velocities for a typical load. So for the Federal 158 gr. .357 personal defense cartridge, Rob’s calculator is giving me 731 J. However, that still isn’t telling me how much kick there is, thanks matt, and I can calculate that myself and compare to the .45 so I know what to expect. Thanks guys & gals!!
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