# need help with bullet drop calculation

#### ar1458

##### Member
here is the problem : I have my gun sighted in at 200 yards but I do not have a range pass 200 yards ... My gun is a sako .300 win mag , shilen barrel 26'' muzzle break ..ammo is handload 168 grain berger VLD , RL-22 powder at 3055 fps ..scope is a zeiss conquest Z-plex 6.5-20x50mm target turrets .. I will be sighting this gun in KANSAS for 300,400, 500 yards when I arrive but to save on ammo I would like to know how much bullet drop at those yards ..the turret right now is set at ZERO for 200 yards ...if you can get me close that would save time and ammo ... or tell me how many clicks for 300,400, and 500 yards ....thanks

#### royinidaho

##### Well-Known Member
To get a little more than just in the ball park a piece of information is needed.

This data would be the distance in inches between the line of bore and line of sight.

To get this:

1. measure the diameter of the scope end bell at the end.
2. measure the diameter of the barrel at the end of the scope end bell.
3. measure the distance between the top of the end bell and the bottom of the barrel at the end of the end bell.
4. Subtract 1/2 of end bell diameter AND 1/2 of the barrel diameter from the top of end bell to bottom of barrel measurement.
This will give you the line of sight about the line of bore distance, fairly close.

Finally go here and punch in your data. In short order you'll have your numbers. JBM - Calculations - Trajectory

#### Mikecr

##### Well-Known Member
If you can't figure this at the range, how do you plan to do it in the field?

#### ar1458

##### Member
If you can't figure this at the range, how do you plan to do it in the field?
practice first,then hunt

#### LRSickle

##### Well-Known Member
I use nearly the same method to determine scope height as you do Roy, however I measure the diameter of the bolt and the diameter of the scope tube nearest the turrets. Now you got me wondering. If you have a 20moa ramp would it make any difference measuring out on the bell vs near the turret? Or is that just really really splitting hairs?

#### Mikecr

##### Well-Known Member
practice first,then hunt
Practice asking on a forum what to dial for a given range?

I guess with the right cellphone service you could come back and ask before each shot...
But have you considered learning how to do it, and practicing to a point of proficiency?

Why should anyone throw them to you?

#### royinidaho

##### Well-Known Member
LRSickle

I wonder the same thing as I have a 40 moa rail on this one but figure I'll fudge the value when doing the drop chart.

Also, yur not in the prry phone book.

Check your PM I'll send you one in a moment.

#### ar1458

##### Member
To get a little more than just in the ball park a piece of information is needed.

This data would be the distance in inches between the line of bore and line of sight.

To get this:

1. measure the diameter of the scope end bell at the end.
2. measure the diameter of the barrel at the end of the scope end bell.
3. measure the distance between the top of the end bell and the bottom of the barrel at the end of the end bell.
4. Subtract 1/2 of end bell diameter AND 1/2 of the barrel diameter from the top of end bell to bottom of barrel measurement.
This will give you the line of sight about the line of bore distance, fairly close.

Finally go here and punch in your data. In short order you'll have your numbers. JBM - Calculations - Trajectory
this chart works great ...berger bullets also had a chart I was not aware of and all the numbers I calculated with the two charts are close so I have a solid starting point ...thank you ..hopefully some trophy pics next week to follow...

#### royinidaho

##### Well-Known Member
Happy to be of service

#### LouBoyd

##### Well-Known Member
I use nearly the same method to determine scope height as you do Roy, however I measure the diameter of the bolt and the diameter of the scope tube nearest the turrets. Now you got me wondering. If you have a 20moa ramp would it make any difference measuring out on the bell vs near the turret? Or is that just really really splitting hairs?

If you're really splitting hairs the measurements used in most computer programs are referenced to the rifles bore at the muzzle. The distance you want in the calculations is the distance between a line from center of the objective lens to the center of the zero target, then perpendicular from that line to the center of the barrel's crown. That is the distance below the line of sight where the bullet is free to begin it's trajectory.

There is no situation where the bore and zero line of sight are parallel. The error in measuring from the scope to the chamber increases as the angle increases.