Muzzle energy question


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bushmaster1313
January 22, 2013, 12:24 AM
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.

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rcmodel
January 22, 2013, 12:39 AM
Dropping the bullet weight does not = higher velocity, unless the powder charge (Ejecta) is increased.

Here, I'll let you do the hard work of plugging in the numbers:
(You might need a reloading manual to find out the powder charge that equals the same velocity with a lighter bullet.weight

http://www.handloads.com/calc/quick.asp

rc

CraigC
January 25, 2013, 10:35 AM
Does the increase in velocity (squared) make up for the decrease in mass?
Never. Folks have been trying to make up for mass with velocity for 100yrs.

Onewolf
January 25, 2013, 11:12 AM
So dropping the mass to near zero won't allow the velocity to reach near lightspeed and create a time machine?

cfullgraf
January 25, 2013, 11:54 AM
Only with enough propellant.

tbob38
January 25, 2013, 01:43 PM
"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. "

The velocity does go up, but the pressure drops which means that the efficiency also goes down. I would expect that the muzzle energy also have to drop. Some of study of loading tables should show how this works.

Ken70
January 25, 2013, 04:42 PM
Never. Folks have been trying to make up for mass with velocity for 100yrs.
Velocity makes it much easier to hit something when you don't know the exact range. Flatter trajectory with the fast bullet. Big slow bullet has a rainbow like profile for a trajectory.

110 years ago the .30-03 had the heavy bullet. .30-06 went to a lighter bullet. This was because the US had learned about what the Germans and French were doing with their ammo.

popper
January 25, 2013, 05:03 PM
Like RCmodel says, but more important is terminal energy.

56hawk
January 25, 2013, 09:50 PM
It just so happens that I tested this recently. I was loading 44 magnum for use in a rifle for cowboy action shooting. Tried bullets from 205 to 300 grains. Was using Bullseye starting at five grains and working up. Ended up shooting all the different bullets with five and seven grains, so that's what I graphed for you.

As you can see, the velocity does increase as the bullet weight decreases. Energy was almost a constant for the five grain load, but did increase for heavier bullets with the seven grain load.

http://www.thehighroad.org/attachment.php?attachmentid=178402&d=1359164457

Lost Sheep
January 26, 2013, 04:27 AM
That's a good question, but the question is not that simple if you want results on the target (terminal ballistics).

What the bullet does to the animal, person, steel plate, bowling pin, newpaper, phone book or ballistic gelatine that it hits depends on more factors than just energy. Bullet construction and shape makes a difference. Bullet momentum as well as energy affect results as well.

Doctoral dissertations representing years of research have been written on the matter.

Good luck. Thanks for asking our advice. Sorry I don't have a more definitive answer.

Lost Sheep

Rory McCanuck
January 26, 2013, 04:53 AM
The other part of it is, the lighter bullet loses velocity (and thus, energy) faster than a heavier bullet.
Very soon downrange, the heavier bullet will actually overtake the lighter.

Lost Sheep
January 26, 2013, 05:41 PM
The other part of it is, the lighter bullet loses velocity (and thus, energy) faster than a heavier bullet.
Very soon downrange, the heavier bullet will actually overtake the lighter.
Interesting. How soon? Just one example will do.

Two bullets with the same muzzle energy departing the firing line at exactly the same instant, the faster bullet will reach the 1 foot mark first, of course. The lighter, faster bullet will keep increasing its lead until it sheds enough velocity to match the heavier, slower bullet. At that point the lead will be decreasing. The lighter bullet may reach zero velocity first, but I doubt if the heavier bullet will ever actually pass the location of the lighter bullet anywhere on its flight path. Remember, they have the same muzzle velocity and general shape (no drag parachutes on the lighter bullet).

I could be wrong, as I have not done the math. But it seems to me that the head start of higher velocity would be hard to overcome.

Lost Sheep

savanahsdad
January 26, 2013, 06:22 PM
if you 2X your weight you 2X your energy if you 2X your speed you 4X your energy, you'er droping 25grs from 150 to 125 so that % divided 4 would give you the % of speed you would need to go up just to be the same , you can load down a lighter round and load up a heaver round to hit the same spot ,but the hever round will have more energy, the only way to get more energy out of a lighter bullet is to go with another Cal. (ie. 30-06 175gr -vs- 150gr 300H&H , or a 270win -vs- 270wsm, a lighter bullet in a 270WSM will have mor energy than a heaver bullet in a 270win becaus it can push it faster ,,,,, ok now I have a headache !!

savanahsdad
January 26, 2013, 06:26 PM
The other part of it is, the lighter bullet loses velocity (and thus, energy) faster than a heavier bullet.
Very soon downrange, the heavier bullet will actually overtake the lighter.
maybe in Canada,,,, but in the rest of the world the smaller faster bullet always gets there first

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