raymond s benden
New member
130 gr bullet~3"high @ 100 will be dead on @ 285 -12 at 400. http://www.ballisticstudies.com/Knowledgebase/.270+Winchester.html
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Bullet Drop Questions
- Thread starter ColorNotColour
- Start date
cosletdecoy
New member
I am not sure I understand the first part of your response. "Bullets do rise from barrel but are still actually dropping " how can this be? You are elevating your rifle to hit a certain point. If you don't mind me asking also how much higher at 300 yds were you than zero in point. I do know the higher the scope above barrel there is more room for error on personal level (eyes, focal point, etc) not wanting to create a argument just trying to figure out the situation of hitting higher at that range.
Varminterror
New member
It's winter time, so somebody is playing basketball SOMEWHERE just about everywhere in the country. Go sit 5-15 rows up from the floor such that you're somewhere between head level of the players and level with the basket, and pick a seat down at one end or the other, sooner or later someone is going to shoot a 3point shot.
You'll note that the ball goes ABOVE THE SHOOTER'S HEAD and that it also goes ABOVE THE RIM. Bullets do the exact same thing.
Bullets do not necessarily start dropping as soon as they leave the barrel, but rather they start experiencing downward acceleration (32ft/sec/sec). So we aim above the target such that the vertical component of the shot, so we put a vertical velocity component on our bullets (Vyo = muzzle vel * sin(angle above level)), knowing that the gravitational draw will begin counteracting it immediately after it leaves the barrel. Just like the basketball shot - we gotta throw the ball up above where we want it to hit on the backboard so gravity will bring it back to where we want it.
The physical formula for any shot, only considered by vertical displacement is this:
Y = Yo + Vyo*t + 1/2*a*t^2
Y is the elevation upon impact
Yo is the starting elevation
Vyo = the initial vertical velocity, i.e. the barrel is angled up slightly so it has some vertical velocity initially, again, this is calculated as muzzle vel * sin(angle of barrel)
a is the acceleration, in this case, a = G, acceleration due to gravity, -32.17ft/sec/sec
t in all cases is time, in this case, time of flight
So, if the target is level with the shooter, then Y = Yo, as the bullet will start and end at the same elevation. That leaves us with 0 = Vyo*t + 1/2*a*t^2, or Vyo*t = -1/2*a*t^2, divide by time on both sides, you get Vyo = -1/2*a*t
Substituting in G for a, since a, in this case, is the acceleration of Gravity, "G"
Vyo = -1/2*G*t There's your proof that we HAVE to shoot upward to hit our target, even if was perfectly level with the shooter.
For some real numbers:
6.8rem at 2650fps, with a BC of 400, at 600yrds, that comes out to 0.91sec Time of Flight (t).
Vyo = -1/2 * -32.17 ft/sec/sec * 0.91sec = 14.64ft/sec
So my vertical component needs to be 14.64ft/sec as it leaves the barrel to preempt the gravitational drop.
Just for fun, since the vertical component Vyo = muzzle vel * sin(angle of barrel), 14.64ft/s = 2650 * sin(angle). Sin-1(14.64/2650) = ~19MOA. Add 1.5MOA for a 1.5" sight height with a 100yrd zero, you get ~20.5MOA - my ballistic calculator shows ~21MOA total DROP (not drop below zero) at 600yrds for that particular round.
Another really simple way to learn something for yourself - take a rifle that you have zeroed at 100yrds, and get it on the page at 600. Dial the elevation. Now shoot at 100yrds on a VERY tall target, holding dead on zero. My 6.8SPC will hit about 18" high if I do this. Again, proof that bullets do have to be fired ABOVE the target and have to fly above the line of sight in order to drop back to target.
You'll note that the ball goes ABOVE THE SHOOTER'S HEAD and that it also goes ABOVE THE RIM. Bullets do the exact same thing.
Bullets do not necessarily start dropping as soon as they leave the barrel, but rather they start experiencing downward acceleration (32ft/sec/sec). So we aim above the target such that the vertical component of the shot, so we put a vertical velocity component on our bullets (Vyo = muzzle vel * sin(angle above level)), knowing that the gravitational draw will begin counteracting it immediately after it leaves the barrel. Just like the basketball shot - we gotta throw the ball up above where we want it to hit on the backboard so gravity will bring it back to where we want it.
The physical formula for any shot, only considered by vertical displacement is this:
Y = Yo + Vyo*t + 1/2*a*t^2
Y is the elevation upon impact
Yo is the starting elevation
Vyo = the initial vertical velocity, i.e. the barrel is angled up slightly so it has some vertical velocity initially, again, this is calculated as muzzle vel * sin(angle of barrel)
a is the acceleration, in this case, a = G, acceleration due to gravity, -32.17ft/sec/sec
t in all cases is time, in this case, time of flight
So, if the target is level with the shooter, then Y = Yo, as the bullet will start and end at the same elevation. That leaves us with 0 = Vyo*t + 1/2*a*t^2, or Vyo*t = -1/2*a*t^2, divide by time on both sides, you get Vyo = -1/2*a*t
Substituting in G for a, since a, in this case, is the acceleration of Gravity, "G"
Vyo = -1/2*G*t There's your proof that we HAVE to shoot upward to hit our target, even if was perfectly level with the shooter.
For some real numbers:
6.8rem at 2650fps, with a BC of 400, at 600yrds, that comes out to 0.91sec Time of Flight (t).
Vyo = -1/2 * -32.17 ft/sec/sec * 0.91sec = 14.64ft/sec
So my vertical component needs to be 14.64ft/sec as it leaves the barrel to preempt the gravitational drop.
Just for fun, since the vertical component Vyo = muzzle vel * sin(angle of barrel), 14.64ft/s = 2650 * sin(angle). Sin-1(14.64/2650) = ~19MOA. Add 1.5MOA for a 1.5" sight height with a 100yrd zero, you get ~20.5MOA - my ballistic calculator shows ~21MOA total DROP (not drop below zero) at 600yrds for that particular round.
Another really simple way to learn something for yourself - take a rifle that you have zeroed at 100yrds, and get it on the page at 600. Dial the elevation. Now shoot at 100yrds on a VERY tall target, holding dead on zero. My 6.8SPC will hit about 18" high if I do this. Again, proof that bullets do have to be fired ABOVE the target and have to fly above the line of sight in order to drop back to target.
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Rick Finsta
New member
For those who still can't visualize this, Mythbusters did a great "bullet dropped versus bullet shot" comparison and demonstrated the concept perfectly. It is on Netflix for those so inclined.
Maximum Point Blank Zero is how I recommend any 300yd or in hunting setup with a standard centerfire caliber and barrel length be zero'd. We deal with this a lot during rifle sight in clinics at the club (for gun deer season but the bullet doesn't know what it is traveling to and *hopefully* hitting). Once you go past that you likely need a *calibrated* BDC reticle or a MOA/MOA or MIL/MIL scope capable of quick adjustment of the turrets. Personally I don't care much for BDC reticles as a MIL DOT system is superior IMHO.
For those who are really interested in the subject matter, there is no better book than the 2nd edition of Bryan Litz' "Applied Ballistics for Long Range Shooting."
And since several people mentioned it, if you have the ability to shoot out to where your bullet is just starting to go trans-sonic (around 1340fps is a good target) you can "true" ballistics calculators to your load/gun. So no need to shoot at varying distances per se, many quality calculators will allow you to perform this single test to bring the results in line with reality.
And that is the most important part - "the bullet doesn't lie."
Maximum Point Blank Zero is how I recommend any 300yd or in hunting setup with a standard centerfire caliber and barrel length be zero'd. We deal with this a lot during rifle sight in clinics at the club (for gun deer season but the bullet doesn't know what it is traveling to and *hopefully* hitting). Once you go past that you likely need a *calibrated* BDC reticle or a MOA/MOA or MIL/MIL scope capable of quick adjustment of the turrets. Personally I don't care much for BDC reticles as a MIL DOT system is superior IMHO.
For those who are really interested in the subject matter, there is no better book than the 2nd edition of Bryan Litz' "Applied Ballistics for Long Range Shooting."
And since several people mentioned it, if you have the ability to shoot out to where your bullet is just starting to go trans-sonic (around 1340fps is a good target) you can "true" ballistics calculators to your load/gun. So no need to shoot at varying distances per se, many quality calculators will allow you to perform this single test to bring the results in line with reality.
And that is the most important part - "the bullet doesn't lie."
Paul Heppner
New member
Your scopes are not and should never be mounted parallel to the centerline of your bore in a vertical plane. The centerline of the bore is always angled up with the vertex of that angle somewhere out in front of you. Gravity starts to act on the projectile the instant it exits the bore hence it "drops" away from that centerline instantly. You "sight in" for a desired distance by changing that scope/bore angle with the internal adjustments on the scope. If you run out of adjustment like the guys that shoot goofy distances (1000 plus) then you get your self a scope base with more angle built into it. It's mostly geometry with a little physics thrown in to keep it interesting. I personally prefer to get closer.
OldTurtle
Moderator - Deceased
ColorNotColour....Pull up the JBM Ballistic Calculator on the web and feed in the appropriate information for the round you are shooting and specify the minimum/maximum ranges and the increments with which you are interested...When you hit calculate it will give you a pretty general idea of your trajectory....i/e, bullet drop
Then take that information to the range and set up a few targets at various ranges and without changing your optic settings, shoot at the various targets, always aiming at the bulls eye...You will find out a lot of information about your cartridge, optic, and it's really good experience for learning about what capabilities you have present...
Then take that information to the range and set up a few targets at various ranges and without changing your optic settings, shoot at the various targets, always aiming at the bulls eye...You will find out a lot of information about your cartridge, optic, and it's really good experience for learning about what capabilities you have present...
This is the time that i miss Catshooter. lol
Those trying to tell you about bullet rise, it doesn't happen.. If you stuff a laser in the bore and turn it on and draw a line. Fire a bullet, rise would be that bullet going above that line, and that does not happen. Like your scope, a laser is line of sight. Which is the trick. Getting the scope to show you where the bullet will be.
The bullet when fired is going to do the same thing every time, within the Standard Deviation of the components involved (rifle, bullets, powder... ect)
Where the challenge falls, as the orginal question asked, is how to get the scope and bullet in sync.
What most of these posts are talking about is setting the scope within reasonable limits. Which, will vary depending on shooting experience and preferences.
What is easier to tell someone is that you need to take the gun you are shooting.. Shoot what zero you want. shoot farther, and farther, until you shoot as far as you want to be able to shoot a coyote (make notes)..
Look at the numbers and think about what is going to work for you. There are just acceptable limits when hunting vs. bench shooting. I don't care if my bullet is .9" high, dead on at 200, and 3" lower than the cross hairs at 300. What you should be seeing is that by setting your zero at a good distance for you. you take the challenge out of it, or more appropriately the need to think about one more thing when you have a coyote coming in. I don't have to think about it until they are farther than 350 yrds.
I aim at the center of the coyote (height wise) and just about 4" behind the front shoulder. I know that even at 300+ I can aim at the top of Fur (always at fur), and still hit without really having to do anything for wind until it's blowing so hard that they are not coming anyways.
I have plenty going on when hunting, and when a coyote is coming, i like not having to really sit and think about it. Range cards are the trick for anything farther out.
Keep your card simple with range, magnification, and drop.
Those trying to tell you about bullet rise, it doesn't happen.. If you stuff a laser in the bore and turn it on and draw a line. Fire a bullet, rise would be that bullet going above that line, and that does not happen. Like your scope, a laser is line of sight. Which is the trick. Getting the scope to show you where the bullet will be.
The bullet when fired is going to do the same thing every time, within the Standard Deviation of the components involved (rifle, bullets, powder... ect)
Where the challenge falls, as the orginal question asked, is how to get the scope and bullet in sync.
What most of these posts are talking about is setting the scope within reasonable limits. Which, will vary depending on shooting experience and preferences.
What is easier to tell someone is that you need to take the gun you are shooting.. Shoot what zero you want. shoot farther, and farther, until you shoot as far as you want to be able to shoot a coyote (make notes)..
Look at the numbers and think about what is going to work for you. There are just acceptable limits when hunting vs. bench shooting. I don't care if my bullet is .9" high, dead on at 200, and 3" lower than the cross hairs at 300. What you should be seeing is that by setting your zero at a good distance for you. you take the challenge out of it, or more appropriately the need to think about one more thing when you have a coyote coming in. I don't have to think about it until they are farther than 350 yrds.
I aim at the center of the coyote (height wise) and just about 4" behind the front shoulder. I know that even at 300+ I can aim at the top of Fur (always at fur), and still hit without really having to do anything for wind until it's blowing so hard that they are not coming anyways.
I have plenty going on when hunting, and when a coyote is coming, i like not having to really sit and think about it. Range cards are the trick for anything farther out.
Keep your card simple with range, magnification, and drop.
