Chills1994 Posted January 25, 2011 Share Posted January 25, 2011 Kinetic energy is defined as 1/2 the mass times the velocity squared. whereas, power factor is the mass times the velocity...which IIRC, from my physics classes from 21 years ago is basically just momentum. as far as analyzing bullet or ammo performance, to me anyway, it seems intellectually dishonest to square the velocity first....in my opinion, it artificially inflates the figures. what say you? Link to comment Share on other sites More sharing options...
Flexmoney Posted January 25, 2011 Share Posted January 25, 2011 You mean...back when scores were done on paper and times were recorded with a stop watch? I imagine the supply of squares were being used for the space race. :) (Plus...wouldn't that make the 230g hardball look weaker?) Link to comment Share on other sites More sharing options...
Matt Cheely Posted January 25, 2011 Share Posted January 25, 2011 Exactly, it's just easier to figure. Link to comment Share on other sites More sharing options...
Chills1994 Posted January 25, 2011 Author Share Posted January 25, 2011 I know this isn't correct units-wise. in my google search all I ended up getting were metric units for KE... so I just used grains for mass and feet per second for velocity. a 124 grain bullet at 170 PF has to be going 1,371 fps. a 230 grain bullet at the same 170 PF has to be going 739 fps. if I did the math correctly, the 124 grain bullet has a KE equal to 116,537,742 grain feet/seconds. the 230 grain bullet has a KE equal to just 62,803,915 grain feet/seconds. so obviously the 9mm Major round has got to be almost twice the "man-stopper" that the .45 hardball ammo is, right? :-P Link to comment Share on other sites More sharing options...
Chills1994 Posted January 25, 2011 Author Share Posted January 25, 2011 by the way, I heard all the squares from the space program were stockpiled with the slide rules. so if you're in that storage room picking up a square you might as well pick up a slide rule while you're there. Link to comment Share on other sites More sharing options...
Bill Nesbitt Posted January 25, 2011 Share Posted January 25, 2011 Jeff Cooper told us to use power factor, that's why. Link to comment Share on other sites More sharing options...
DeweyH Posted January 25, 2011 Share Posted January 25, 2011 If we used kinetic energy, then a 115gr 9mm at 1087fps has more energy than a 230gr .45 at 718fps. This is the minimum velocity for the 9mm to make minor and the minimum for .45 to make major. 9mm 115gr at 1087 =301.65ft-lb 40 180gr at 917 =336.01 ft-lb 45 230gr at 718 =263.22ft-lb http://www.firearmexpertwitness.com/customguns/calcnrg.html Link to comment Share on other sites More sharing options...
Chris Keen Posted January 25, 2011 Share Posted January 25, 2011 I imagine it's just fun to theorize .... if you're into that sort of thing. But why reinvent the wheel? But mostly, I'd just have to agree with Bill Nesbitt. lol Jeff Cooper told us to use power factor, that's why. Link to comment Share on other sites More sharing options...
outerlimits Posted January 25, 2011 Share Posted January 25, 2011 You young guys don't remember the ballistic pendulum. That was before the chrono surfaced. I can tell you those 38 super rounds couldn't come close to a .45. Just sayin... Link to comment Share on other sites More sharing options...
Matt Cheely Posted January 25, 2011 Share Posted January 25, 2011 You young guys don't remember the ballistic pendulum. That was before the chrono surfaced. I can tell you those 38 super rounds couldn't come close to a .45. Just sayin... That's just because the 38 super was expending its energy ripping apart the bullet, where as the 45 would deform a little and put the rest of the energy into moving the pendulum. Link to comment Share on other sites More sharing options...
Chills1994 Posted January 25, 2011 Author Share Posted January 25, 2011 thanks for the input fellas! oh...no! me? re-inventing the wheel...oh, heck no! I am a firm believer in the K.I.S.S. principle, and PF is so much easier/simpler to use and to calculate. and seems so much more like comparing apples to apples. I am on another forum where there is a discussion about terminal ballistics effects, specifically the FBI bank robber shoot out from 80's and a few of the posters are like "ALL HAIL KINETIC ENERGY!!" And I am left shrugging my shoulders and scratching my head about the whole velocity squared thing. my thoughts are that in the real world (outside of the physics lab) nobody is shot with the square of the velocity of the bullet. anywhooo...I will just leave it at that as far as this thread goes. I don't want to get it closed. again, thanks for running the numbers for me. Link to comment Share on other sites More sharing options...
AlamoShooter Posted January 25, 2011 Share Posted January 25, 2011 Are you trying to fix something that is not broken? And every time I put my carpenters square on a bullet is just falls off Link to comment Share on other sites More sharing options...
Chills1994 Posted January 25, 2011 Author Share Posted January 25, 2011 my usual modus operandi is to fix something until it IS broken, but in this case... heck, no! besides that, if you use your slide rule instead of your square on your bullets you won't have to worry about the bullets falling off. LOL! Link to comment Share on other sites More sharing options...
GForceLizard Posted January 25, 2011 Share Posted January 25, 2011 Chills1994, I'm sure you've already looked this all up but kinetic energy is, well energy. It is the work needed to accelerate a body of a given mass from rest to its stated velocity. The same amount of work is done by the body in decelerating from its current speed to a state of rest. You can kind of see why people at the other discussion would like KE. If you want to accelerate a bullet from 1150fps to 1200fps it takes way more powder (energy) than it did to get from 750fps to 800fps. Adding speed is not linear, it's squared. As for power factor and momentum +1 to Matt Cheely - It's easier to calculate It's a better indicator of steel knock down power. Link to comment Share on other sites More sharing options...
outerlimits Posted January 25, 2011 Share Posted January 25, 2011 Perhaps a better example is shooting second chance. Link to comment Share on other sites More sharing options...
Chills1994 Posted January 25, 2011 Author Share Posted January 25, 2011 Perhaps a better example is shooting second chance. ahhh...man! you're really dating yourself now. first the ballistic pendulum comment and now this....bringing up second chance. I am assuming you mean the bowling pin shoot. @ Gforce, it's squaring the velocity in the KE equation that bugs me. as you can see what was posted up above numbers-wise, the 9mm Para puts out more foot-pounds than that .45ACP, hence, therefore, ergo, all police departments and federal law enforcement agencies should be required to carry the more powerful 9mm pistols. just kidding... .50AE is "good med'cin" for bowling pins. I've seen it with my own two eyes. I felt it too. 9mm Major is anemic. .40 at major power factor is better .45 ACP is next. and some guys are stuffing a cast lead 255 grain boolit meant for the .45 Long Colt into their ACP cases. shot placement is critical with pins. at our pin matches the table is 3 feet deep and the pins are set back a foot and a half from the edge...so you have to knock the pins clear off the table. the timer stops when the last pin falls off the table. you are partner'ed up with another guy who has 5 pins to clear on his side. I get to use my laser grips. :-) Link to comment Share on other sites More sharing options...
P.E. Kelley Posted January 25, 2011 Share Posted January 25, 2011 Perhaps a better example is shooting second chance. Absolutely! Bowling pins "set" their own power factor! I loved shooting pins!!! See ya in Mesa ?! Patrick Link to comment Share on other sites More sharing options...
GForceLizard Posted January 25, 2011 Share Posted January 25, 2011 Because USPSA is a game and not a debate about Marshall & Sanow vs. Fackler Link to comment Share on other sites More sharing options...
Chills1994 Posted January 25, 2011 Author Share Posted January 25, 2011 are you sure you aren't reading the other forum I am talking about? we're treading into forbidden territory here on Enos when you start bringing up those names. I don't want my thread closed down. I am beginning to like that guy Jeff Cooper more and more. I read some "gunzine" the other night. He supposedly advocated being able to hit ping pong balls at 7 yards. I'll have to get around to comparing the upper A zone on a USPSA target to a ping pong ball one of these days. Link to comment Share on other sites More sharing options...
ima45dv8 Posted January 25, 2011 Share Posted January 25, 2011 Jeff Cooper told us to use power factor, that's why. In terms of the original question of why we use PF instead of KE, that covers it pretty well. Link to comment Share on other sites More sharing options...
Chills1994 Posted January 25, 2011 Author Share Posted January 25, 2011 a'yup, that's good enough for me too! Link to comment Share on other sites More sharing options...
XRe Posted January 25, 2011 Share Posted January 25, 2011 The funny thing is, the feeling at the time was that .45 would do a better job on people, and thus Cooper's slant, and why we're more concerned with momentum than we are with energy. In practical terms, though, the data's in, and handguns flat out suck - it doesn't matter what cartridge you're talking about, they're all equally bad. In terms of "what works" in the "real world", power factor is kind of a waste... Sectional density and energy factored together would be a better measure of average penetration, but even that doesn't really matter that much. If you wanted more definitive testing, you'd set a minimum PF to play around 145 for 9mm, 180 for .40, and about 190 for .45, and then make your A-zone about the size of a 4-6 inch circle in the "chest"... thus approximating typical carry loads and a more realistic vital zone... From a game standpoint, though, it's still useful. Arguably, a load with a higher power factor is harder to control than one with a lower power factor (though Open guns are a little bit different deal), so it gives us a measure on relative controllability of the gun (imperfect, granted). To those who say "power factor is easier to calculate"... really? I mean energy requires a couple more keystrokes on the calculator to do it manually, but on anything else (chrono, scoring program, etc), it's just as easy - put in bullet weight and velocity... Link to comment Share on other sites More sharing options...
JeffWard Posted January 25, 2011 Share Posted January 25, 2011 Because the JMB=GOD crowd would have a cow... When it comes to "effectiveness" a picture is worth 1000 words... Source: http://www.m4carbine.net/showthread.php?t=19887 Jeff Link to comment Share on other sites More sharing options...
G-ManBart Posted January 25, 2011 Share Posted January 25, 2011 And I am left shrugging my shoulders and scratching my head about the whole velocity squared thing. my thoughts are that in the real world (outside of the physics lab) nobody is shot with the square of the velocity of the bullet. Give yourself an easier example. Take a .223 55gr bullet going 3,200fps or a .45 230gr bullet going 750fps....pretty obvious that those two are in completely different categories. I've never shot a popper up close (say 25yds or less) with a .223, but I suspect they'll slam one down pretty hard! Energy isn't the only thing that matters, but it does count. R, Link to comment Share on other sites More sharing options...
AlamoShooter Posted January 25, 2011 Share Posted January 25, 2011 Or to state the issue in other forums lingo "So the 45 long colt is the most-est powerfully because in the movie th Quick & the Dead when hit shot they went back-wards 10 to 15 feet and at the end the hole would even show sun light in a shadow rite through a person." "And in the Movie Die-Hard multiple hits with a full Auto 9milly would only make the guy fall down". Soo ThaT! proves IT! Link to comment Share on other sites More sharing options...
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