7 mm Rem. Ultra Mag Range constants?

[rescurat]

Just recieved a new rifle and have been trying to find the range constants for figuring windage (minutes of full wind). I have searched the web, and so far come up dry. If anyone can help with either the constants themselves, or a formula for figuring them my self it would be greatly appreciated.

 

[DANTEC]

try this web site
http://www.eskimo.com/~jbm/ballistics/traj/traj.html

that allow you to compute any thing you need FREE

good shooting

DAN TEC

 

[Ian M]

FULL VALUE WIND ESTIMATION
Here is one that may be useful. You may have to modify it with field testing but it might provide a starting point.


1ST digit of range (100's) X Wind Velocity divided by the constant = Minutes of Angle

Distance Constant
One hundred to five hundred yards 15
Six hundred yards 14
Seven hundred to eight hundred 13
Nine hundred yards 12
One thousand yards 11

 

[speedbump]

Ian's formula is good for a .308/30-06 class of cartridges. A ballistic calculator like the eskimo will get close.

For my 7mmRUM with a 176 Cauterucio @ 3,360fps, I took a .308 Palma chart (155 Palma loads) and divided the MOA listed by 5. That gets me on paper & close at 1,000 yards. Hope this helps.

 

[Michael Eichele]

rescurat,

I am not sure if this would help, but if it does here it is.

An example for calculating wind would be like this: 3000 (range in feet) divided by muzzle velocity(2600)=1.1538 The real time of flight for standard air density would be (at 1000 yards) 1.7651 useing a 168 grain .308 caliber bullet. Then, 10 miles per hour times inches per second (10x17.6)=176.0 Next take the real time of flight and subtract the time of flight as if there was no apmoshere (1.7651-1.1538)=0.6113 This is the delay time, now multiply the delay time by the inches per second (.6113x176)=107.58 inches at 1000 yards

 

[DANTEC]

that seem very difficult to make serious long range shooting without a matched trajectory table and strange because if now we use top fuel caliber in new rifle generation to still want to use Kentuky windage , that enought difficult to read the wind wright to don t add error factor by estimate or use quick formula

a chart stick on the stock really help and avoid mistake , better is to built a small log book with temp cahrt for elevation ,drop chart and windage chart

good shooting

DAN TEC

 

[Michael Eichele]

DANTEC,

Im sorry if that is a difficult formula, if I read his post correctly he was looking for a formula as just a place to start.