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different calibers same weight bullet, different speeeds????Discussion regarding the reloading of ammunition and tuning of loads for accuracy
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foreign Member
Joined: Apr 02, 2008 Posts: 50 Location: NEW ZEALAND
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Posted: Sun Apr 13, 2008 4:00 pm Post subject: different calibers same weight bullet, different speeeds???? |
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i was wondering why a .243 and lets say a .308 with the same bullet weight (105gr) can be sent at different speeds. both have the same case size. or a .22.243 for example. (im assuming thats a .243 necked down to a .22 caliber. just wondering
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Pumpkinslinger Super Member
Joined: Sep 22, 2007 Posts: 5001 Location: NC foothills
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Posted: Sun Apr 13, 2008 6:25 pm Post subject: Re: different calibers same weight bullet, different speeeds???? |
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If the pressure is the same for both cartridges the one with the bigger bore will provide more force to the bullet.
Force = Pressure x Area
More force means more acceleration
Acceleration = Force / Mass
_________________ Mike
"I ain't no better than anybody else, and there ain't nobody better than me!" Ma Kettle |
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gelandangan Super Member
Joined: May 07, 2006 Posts: 6397 Location: Sydney Australia
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Posted: Sun Apr 13, 2008 8:33 pm Post subject: Re: different calibers same weight bullet, different speeeds???? |
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Doing some number juggling with an internal ballistics program gives these results
(for this example, I use 100gn projectile weight)
.243 Win
Projectile .243 100gn Hornady SP 2450
Powder Varget 35 Grains
Barrel 20 inch
C.O.L. 2.650
Muzzle velocity 2647 FPS
Energy 1556 ft.lbs
.308 Win
Projectile .308 100gn Hornady SJ 3005
Powder Varget 35 grains
C.O.L. 2.650 inch
Barrel 20 inch
Muzzle Velocity 2065fps
Energy 947 ft.lbs
_________________ A straight line is the shortest distance between two points.
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