Muzzle Energy Question

[bushmaster1313]

I know that muzzle energy equals 1/2 M V squared

So what happens if everything is kept the same but the bullet weight is dropped from, say, 150 to 125.

The mass goes down but the velocity goes up.

Does the increase in velocity (squared) make up for the decrease in mass?

In other words, with the same barrel and the same amount of the same powder, would the 150 gr or the 125 gr have more muzzle energy?

Thank you in advance.

 

[colt_saa]

If you left the powder charge the same and simply substituted a lighter projectile, energy would drop.

You might want to buy a loading manual or two.

Hand loading is not something that you should be doing off the cuff.

 

[bushmaster1313]

Not going to reload.
Just thinking out loud

 

[Nevada Ed]

Take the velosity of the bullet times its self...950x950 (902500)........

divided by 450240 equals....2.0044864

Times the bullets grs weight ( 125grs)

equals the energy of 250.5608

 

[Titegroups]

IIRC and my memory aint so good anymore, energy is M times v squared. I think the total energy would have to stay the same with the same powder charge. Using the formula small increases in velocity will affect energy delivered much more than bullet weight.

 

[Rule3]

Here ya go. Calculate away!

Energy Calculator

Some go with light and fast, others heavy and slow. Somewhere they are equal.

Would you rather be hit with a 40 grain bullet from a 22 LR or a 223??

 

[Skip Sackett]

In reloading, which I cannot figure out why you are not going to venture into that aspect of our hobby, to each his own, there is very seldom a time when one changes projectile weight and doesn't also change powder charge. So, actually, your question is a fallacy. Oh, there are special use places where you would do what you propose but, you know that going in and are loading for that special use, only.

Case in point: Lighter bullets at subsonic levels coupled with a suppressor is one powder charge while the heavier bullet at full charge is used to shoot longer distances without regard to noise levels.

So, in a normal loading situation, one loads the lighter bullets with MORE powder to gain a flatter trajectory or a heavier bullet with less powder at lower velocities to gain short range knock down power.

Not trying to be mean, but, the question isn't one that most hand loaders deal with, usually we go to lighter bullets for a reason and that reason is usually to push them harder and gain something by doing so.

Oh, because of the difference in mass, the heavier bullet will carry more of it's energy further downrange than a lighter bullet. It takes a bigger arc to get there but, when it gets there, it hits with a bit more effectiveness.

 

[Skip Sackett]

I forgot one thing, BC. Ballistic coefficient takes bullet weight into consideration. A heavy bullet usually has a better BC than a lighter one of the same caliber. Here are two printouts of different bullets from my 358WSSM. The first is from a 200gr Accubond while the second is from its 225gr bigger brother. Both loaded to the same velocity.




As you can see, the heavier one retains velocity and power down range but has a bit more of an arc to get there.

I hope that makes sense....

 

[Skip Sackett]

I guess I will post one more picture though.
Notice what happens when you load the lighter bullet to it's potential:


Now that lighter bullet is going 150fps faster at the muzzle. I realize down range benefits too. At 350 yards I have much less drop and an animal is not going to notice the difference in the loss of ftlbs. The difference between a 225gr bullet at 1850fps and a 200gr at the same velocity probably cannot be felt!

 

[fds5116]

It Depends

Some powders operate best at low pressures; if you keep the powder and the charge the same, it is likely that the lighter bullet will extract more energy out of the powder charge, as the heavier bullet will make the pressure go up, perhaps out of the pressure range that the powder works best in.

Other powders operate best at high pressures; in that case, I'd expect the heavier bullet to use the energy of the charge more efficiently.

In a 357 magnum, for instance, the efficiency (muzzle energy divided by powder weight, in this case) for a 110 grain and a 180 grain bullet will be different, and different for each powder. Put a small charge of Bullseye under each one, then a max charge of H110 under each one. You will get different answers.

The one answer you won't get is that the muzzle energy is the same!

So, it depends...
cheers