HI Dave this one is for you LOL I did not want to hijack the other thread !! LOL
You seam to be the technical guy about spin and bullet length so can you tell me this one please thanks.
You have a 40 cal bullet .408 x 430.9 grains x 1.4185 long moving at 1235 fps
will this be stable and what are your calculations and thoughts thanks looking forward to your reply take care
SchuetzenDave
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Re: SchuetzenDave
Caliber 0.408 Inches
Bullet Weight 430.9 Grains
Bullet Length 1.4185 Inches
Barrel Twist 16 Inches/turn
muzzle velocity 1235 fps
Temperature 50 degrees Fahrenheit (59 is standard)
Pressure 29.92 inches of mercury (29.92 is standard)
Sg = 2.03
She will work out fine in a 16:1 twist barrel.
Bullet Weight 430.9 Grains
Bullet Length 1.4185 Inches
Barrel Twist 16 Inches/turn
muzzle velocity 1235 fps
Temperature 50 degrees Fahrenheit (59 is standard)
Pressure 29.92 inches of mercury (29.92 is standard)
Sg = 2.03
She will work out fine in a 16:1 twist barrel.
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Re: SchuetzenDave
Thanks Dave dont know where or how you come up with your numbers but good to know thanks take care and stay warm winter is here again
- bpcr shooter
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Re: SchuetzenDave
NMLRA Member
Winnequah Gun Club Member (Lodi, Wi)
WIFORCE Member
SCI Member
Winnequah Gun Club Member (Lodi, Wi)
WIFORCE Member
SCI Member
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Re: SchuetzenDave
Thanks bpcrshooter i will check that out when i have time. Keep shooting and having fun
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Re: SchuetzenDave
I use the Don Miller gyroscopic stability factor calculation.
An explanation of his method is explained by him here:
https://bisonballistics.com/Miller-How- ... -Twist.pdf
Ballistics programs assume your are using a bullet that is gyroscopically stable for your barrel's twist.
Therefore you need to confirm your bullet is gyroscopically stable before you entertain using a ballistics program.
Here you can enter your data to calculate your gyroscopic stability factor:
https://bisonballistics.com/calculators/stability
An explanation of his method is explained by him here:
https://bisonballistics.com/Miller-How- ... -Twist.pdf
Ballistics programs assume your are using a bullet that is gyroscopically stable for your barrel's twist.
Therefore you need to confirm your bullet is gyroscopically stable before you entertain using a ballistics program.
Here you can enter your data to calculate your gyroscopic stability factor:
https://bisonballistics.com/calculators/stability
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Re: SchuetzenDave
ok so does it tell you at what ranges it will be good for ? thanks
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Re: SchuetzenDave
For distance implications you need to calculate dynamic stability (once you have confirmed if your bullet is gyroscopically stable).
Dynamic stability is dependent on center of gravity of your bullet and nose shape which changes the yaw angle and increases the bullets susceptibility to wind drift.
However increased velocity stabilizes the yaw and 1300 to 1400 fps is usually sufficient velocity to compensate for velocity losses over longer distances.
So with slow moving black powder bullets drag is important over long distance since drag can reduce velocity and impact the yaw stability so the bullet starts to tumble before reaching the target.
Pointier bullets have the center of gravity further back so they have more of a yaw angle which requires more velocity to stabilize them and they are more critical to velocity losses over long distances due to drag.
Money bullets are a bit more pointier than Creedmoor style bullets and I have found they lost their dynamic stability in my .40-65 at 500 yards if I am below 1250 fps.
Going over 1250 fps allows me to stabilize the yaw of my Money bullet out to 1,000 yards.+
Dynamic stability is dependent on center of gravity of your bullet and nose shape which changes the yaw angle and increases the bullets susceptibility to wind drift.
However increased velocity stabilizes the yaw and 1300 to 1400 fps is usually sufficient velocity to compensate for velocity losses over longer distances.
So with slow moving black powder bullets drag is important over long distance since drag can reduce velocity and impact the yaw stability so the bullet starts to tumble before reaching the target.
Pointier bullets have the center of gravity further back so they have more of a yaw angle which requires more velocity to stabilize them and they are more critical to velocity losses over long distances due to drag.
Money bullets are a bit more pointier than Creedmoor style bullets and I have found they lost their dynamic stability in my .40-65 at 500 yards if I am below 1250 fps.
Going over 1250 fps allows me to stabilize the yaw of my Money bullet out to 1,000 yards.+