45 acp bullet drop?
This is a discussion on 45 acp bullet drop? within the Defensive Carry Guns forums, part of the Defensive Carry Discussions category; A bullet of a certain weight will fall at the same rate no matter what gun is used or what its velocity.
The drop of ...

August 4th, 2009 01:22 PM
#16
Senior Member
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A bullet of a certain weight will fall at the same rate no matter what gun is used or what its velocity.
The drop of a 230gr bullet fired at 1000 fps from a 5 inch 1911 will be the same if it was fired from a 2 inch snubbie at 750fps, IF both bullets travel the SAME amount of TIME from muzzle to target.
230 gr 1000fps target 100 yards Muzzle to target Approx: .3sec
230 gr 500fps target 50 yards Muzzle to target Approx: .3sec
Both bullets will drop the same amount as a bullet of the same weight will drop the same distance if allowed to fall from your hand for .3sec..
Gravity determines the velocity the bullet falls, with that and the time the bullet is in flight you can determine the drop in trajectory.
bosco

August 4th, 2009 09:29 PM
#17
Lead Moderator
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Originally Posted by
boscobeans
A bullet of a certain weight will fall at the same rate no matter what gun is used or what its velocity.
The drop of a 230gr bullet fired at 1000 fps from a 5 inch 1911 will be the same if it was fired from a 2 inch snubbie at 750fps, IF both bullets travel the SAME amount of TIME from muzzle to target.
230 gr 1000fps target 100 yards Muzzle to target Approx: .3sec
230 gr 500fps target 50 yards Muzzle to target Approx: .3sec
Both bullets will drop the same amount as a bullet of the same weight will drop the same distance if allowed to fall from your hand for .3sec..
Gravity determines the velocity the bullet falls, with that and the time the bullet is in flight you can determine the drop in trajectory.
bosco
Sounds good in theory.
In reality its the ballistic coefficient of the bullet that makes the difference. How it "slices" through the air.
That dose'nt always correspond to the theoretical charts, that is why it is important to test fire each load, log it, and know how that load shoots in that particular gun.
No big deal on a handgun, but if you are shooting arifle for small groups at long ranges it makes a big difference.
Universal
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August 4th, 2009 09:40 PM
#18
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Bullet drop according to the JBM ballistic calculator using said example with a time of flight of .3 seconds at 100 yards.
230gr. 1000 FPS...11.9 inches of drop at 100 yards, sighted at 25 Time of flight at 100 yards .306
230 gr. 500 FPS.....8.8 inches of drop at 100 yards, same as above. Time of Flight .308 sec
What changed? The ballistic coefficient of the same bullet traveling at different speeds.
Not a lot of difference at 100 yards, but a big difference on out there.
Here is the calculator for those that want to play with it...
JBM  Calculations
BTW, I used 1 yard increments for the calcs.
Universal
Background
Checks...the next step towards registration and confiscation.
AR. CHL Instr. 07/02 FFL
Like custom guns and stuff? Check this out...
http://bobbailey1959.wordpress.com/

August 5th, 2009 12:43 AM
#19
Senior Member
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"230gr. 1000 FPS...11.9 inches of drop at 100 yards, sighted at 25 Time of flight at 100 yards .306
230 gr. 500 FPS.....8.8 inches of drop at 100 yards, same as above. Time of Flight .308 sec"
One had double the velocity and they both had the same time of flight ( off by .002) over the same distance..??
The bullet that moved at 1000fps had about 1.5 times the drop at the same distance with the same bullet as the one moving at 500fps..???
Might work out with the calculator but I know that when I load the same bullet to different velocities I have to hold a bit higher on my target with the slower bullet. OMO
bosco

August 5th, 2009 01:24 AM
#20
VIP Member
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Originally Posted by
boscobeans
A bullet of a certain weight will fall at the same rate no matter what gun is used or what its velocity.
The drop of a 230gr bullet fired at 1000 fps from a 5 inch 1911 will be the same if it was fired from a 2 inch snubbie at 750fps, IF both bullets travel the SAME amount of TIME from muzzle to target.
230 gr 1000fps target 100 yards Muzzle to target Approx: .3sec
230 gr 500fps target 50 yards Muzzle to target Approx: .3sec
Both bullets will drop the same amount as a bullet of the same weight will drop the same distance if allowed to fall from your hand for .3sec..
Gravity determines the velocity the bullet falls, with that and the time the bullet is in flight you can determine the drop in trajectory.
bosco
Sorry, but your theory only works in a vacuum. In the real world, there are two external forces acting on the bullet. Gravity and air resistance. Ambient temperature, barometric pressure and altitude also have an effect but in relation to the air density.
Here are a couple of charts done with the external ballistics calculator in RCBS Load. All criteria are the same except for the distance (100 yds. for the first chart and 50 yds. for the second) and a minor variation in flight time but it's close enough with rounding to meet your .3 second flight time (318 ms for the first chart and 306 ms for the second).
1000 fps  100 yds.  flight time 318 ms  12.18" drop
500 fps  50 yds.  flight time 306 ms  7.54" drop
Hotguns  you and I must be looking at two totally different things as I can't figure out where your numbers come from.
Hoss
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August 5th, 2009 07:59 AM
#21
Senior Member
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cvhoss,
"Sorry, but your theory only works in a vacuum. In the real world, there are two external forces acting on the bullet. Gravity and air resistance. Ambient temperature, barometric pressure and altitude also have an effect but in relation to the air density."
You are absolutely correct. All the variant factors you have listed above will affect the bullet in flight. They all affect the velocity of the bullet. They all will contribute to the slowing down of the bullet as it plows its way through the air. Altitude will play a role in measuring gravitational pull but it so minor as to be insignificant when dealing with the mass of a bullet.
The wind resistance affecting the drop due to gravity is almost a nonfactor since a bullet will rarely (except maybe for some extreme long range shooting) be in flight long enough to measure any resistance in a drop. It takes a 9mm bullet a good distance before it reaches around 125mph which for a 124gr bullet is about its maximum velocity in a free fall.
"Gravity determines the velocity the bullet falls, with that and the time the bullet is in flight you can determine the drop in trajectory." This is just a crude but somewhat accurate way of looking at trajectory that might be helpful for some people to get a better understanding of how a bullet travels from point A to point B.
bosco
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