A Round With 3,250 fps Muzzle Velocity, And Weighing 6,096 grains?
- Thread starter Charley C
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45_auto
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Pete D said:
If you're impressed by 150,000 ft-lbs of energy, go watch a few pickup trucks or SUV's drive by at 30 MPH. They'll each have about 150,000 ft-lbs of energy! On the freeway at 70 MPH, they're at about 850,000 ft-lb.
Even easier, go pick up a flashlight that uses 3 D-cells. You'll be holding about 180,000 ft-lb of energy! The D cells have about 60,000 ft-lb each.
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White Walker
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Even more incredible is a 120mm main gun round from a tank. The round travels well over one mile per second. That's over 5,280 feet per second. Pretty fast.
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If you want scary energy numbers look at depleted uranium armor penetrators.
Many pounds of metal at high velocity.
The 'steps' you see on large artillery barrels allow for pressures well over the bursting point of a plain steel barrel.
By shrinking the outer layers onto the inner ones the steel is placed under huge compressive forces.
The inner steel rings do not see hoop stress (causes burst failures) until the internal pressure cancels the already present compressive force from the outer layers.
Many pounds of metal at high velocity.
The 'steps' you see on large artillery barrels allow for pressures well over the bursting point of a plain steel barrel.
By shrinking the outer layers onto the inner ones the steel is placed under huge compressive forces.
The inner steel rings do not see hoop stress (causes burst failures) until the internal pressure cancels the already present compressive force from the outer layers.
Blade First
Member
Quick estimate for muzzle energy...will get you very close [i.e., usually < 1 ft.lb. of variance]:
Energy (in ft.lbs) = (muzzle velocity)(muzzle velocity) x bullet weight (in grains) divided by 450,450 (a constant that's easy to remember)
For one of my .357SIG loads, the calc. is:
1450 fps x 1450 fps x 125 grains / 450,450 = 583.44 ft.lbs.
Speed kills!
Energy (in ft.lbs) = (muzzle velocity)(muzzle velocity) x bullet weight (in grains) divided by 450,450 (a constant that's easy to remember)
For one of my .357SIG loads, the calc. is:
1450 fps x 1450 fps x 125 grains / 450,450 = 583.44 ft.lbs.
Speed kills!
Gaucho Gringo
Member
Wonder how many rounds the 30mm barrels of the A-10 are rated for? It seems like traditionally the larger the bore of a barrel, the less rounds they will take. An example:the 16" naval guns were rated for around 275-400 rounds depending on model before they needed to be replaced compared to the 5" naval guns were rated for around 5,000-10,000 rounds depending on model before they needed to be replaced. Just curious.
herrwalther
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Well when you can fire up to 4200 rounds per minute, barrel life would be high in number of rounds just so you can get off more bursts. From what my google-fu says, the USAF specified that each barrel must have a minimum round life of 21,000 rounds. With 7 barrels going at max fire rate, and weight/space of ammo, heat etc you would wear out the barrels in 35 minutes of sustained fire.
Charley C
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24 C-130 Hercules Taxiing In A tight Group
Devonai........
Being a "Herk" guy.....have you seen the amazing photo that's been all over Yahoo of the 24 Herks taxiing in a tight group, about to take off in a group?
I copied the image, intending to post it but I haven't figured out how to post photos yet; then I started to copy and paste the URL to the page......it was on my Chrome browser and I was using Firefox.......
Devonai........
Being a "Herk" guy.....have you seen the amazing photo that's been all over Yahoo of the 24 Herks taxiing in a tight group, about to take off in a group?
I copied the image, intending to post it but I haven't figured out how to post photos yet; then I started to copy and paste the URL to the page......it was on my Chrome browser and I was using Firefox.......
Charley C
Member
Gaucho Gringo........
The article on Wiki about the GAU-8 tells all about barrel life, etc; I think I posted a link to it, but if not, the article will come right up if you google GAU-8 Avenger canon.
The article on Wiki about the GAU-8 tells all about barrel life, etc; I think I posted a link to it, but if not, the article will come right up if you google GAU-8 Avenger canon.
Mountainman38
Member
The formula used to calculate kinetic energy (the energy of an object in motion) is:
K.E. = (1/2)(mass)(velocity^2).
To end up with units of force, we have to convert mass to force.
Mass has to be in lbm (pound mass), and velocity in feet per second.
To convert grains to lbm, take mass(in grains) times 1 lbm/7,000 grains, times 1 lbf/32.2 lbm*ft/s^2.
This gives a kinetic energy for the OP's round of:
K.E. = (1/2)(6,096 gr * 1 lbm/7,000 gr * 1 lbf/32.2 lbm*ft/s^2)(3,250 ft/s)^2
After canceling units, we have K.E. = 142,832 lbf*ft.
Mountainman38
Member
I'm curious about what you're referring to here. We've been talking about kinetic energy, so unless you're swinging that Maglite pretty quick, I'm not sure where the 60,000 ft*lb of energy comes from. Are you referring to chemical energy?
moxie
Member
Mountainman, good catch. I left off the .5 in front of mass using this infernal iphone. Also couldn't type the squared in superscript. Thanks for correction.
Mountainman38
Member
Moxie,
Sorry if it came off like I was trying to correct you. I wondered for a long time how the energy figures for a particular cartridge were calculated, so finally took the time to look it up. Just figured I'd pass the formula along.
Sorry if it came off like I was trying to correct you. I wondered for a long time how the energy figures for a particular cartridge were calculated, so finally took the time to look it up. Just figured I'd pass the formula along.
Mountainman38
Member
brickeyee,
Not sure what you're trying to correct here. Weight is mass being acted on by gravity, and gravity is a force, if that's what you mean.
What would you just use mass (slugs) for? Bullets are generally measured in grains or pounds, which is not mass, and so must be converted.
Tanshanomi
Member
I'm not sure how good it would be for Bear defense. It's really more tailored to ground assault, and there are better defensive options for big, high altitude bombers like that.
moxie
Member
Mountainman,
Far from being a problem, I welcome the correction. I'm of the opinion that anyone who throws data out on this board should be willing to be corrected when there is an obvious mistake.
Far from being a problem, I welcome the correction. I'm of the opinion that anyone who throws data out on this board should be willing to be corrected when there is an obvious mistake.
230RN
2A was "political" when it was first adopted.
Hatcher has it as
f/s X f/s X grains / 450,240
That denominator contains factors for conversion to other units and assumes an average value for local gravity and varies slightly with authors.
For ease of recollection, I just use 450,000 and get within about a half percent of published data:
450,000 / 450,240 = 0.99946; 0.99946 X 100 = 99.946%
Considering the variations in velocity from shot to shot, that's usually close enough for me unless I'm launching a missile to hit a comet after an umpteen billion mile trip.
Terry, 230RN
More (variation of gravity (g) over the earth's surface:
http://en.wikipedia.org/wiki/Gravity_of_Earth#mediaviewer/File:Geoids_sm.jpg
See also:
http://en.wikipedia.org/wiki/Standard_gravity
f/s X f/s X grains / 450,240
That denominator contains factors for conversion to other units and assumes an average value for local gravity and varies slightly with authors.
For ease of recollection, I just use 450,000 and get within about a half percent of published data:
450,000 / 450,240 = 0.99946; 0.99946 X 100 = 99.946%
Considering the variations in velocity from shot to shot, that's usually close enough for me unless I'm launching a missile to hit a comet after an umpteen billion mile trip.
Terry, 230RN
More (variation of gravity (g) over the earth's surface:
http://en.wikipedia.org/wiki/Gravity_of_Earth#mediaviewer/File:Geoids_sm.jpg
See also:
http://en.wikipedia.org/wiki/Standard_gravity
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"What would you just use mass (slugs) for? Bullets are generally measured in grains or pounds, which is not mass, and so must be converted."
You convert grains to pounds and then divide by g to get slugs.
Many of the 'simplified' formulas have all those conversions bult into teh denominator.
32.2 ft/s^2, 7,000 grains/pound, 1/2.
All works out to 450,800
Rnergy (ft/lbf) = weight (grains) x velocity (ft/s) x velocity (ft/s) / 450,800
An 8 pound DU penetrator at 5,000 ft/s comes out over 3 million ft/lb
And DU is pyrophoric. It burns.
You convert grains to pounds and then divide by g to get slugs.
Many of the 'simplified' formulas have all those conversions bult into teh denominator.
32.2 ft/s^2, 7,000 grains/pound, 1/2.
All works out to 450,800
Rnergy (ft/lbf) = weight (grains) x velocity (ft/s) x velocity (ft/s) / 450,800
An 8 pound DU penetrator at 5,000 ft/s comes out over 3 million ft/lb
And DU is pyrophoric. It burns.
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