Bullet drop question

[KLR1968]

Here is the situation. I am shooting a 308 Winchester. Bullet is a Hornady 165g SST, velocity is 2741 fps. I am getting good solid 1/2 MOA groups at 100 yds. When I move out to 200 yards, I should have a bullet drop of about 3.5 inches. Instead, I am getting 5.5 inches, every single time. All these programs can't be wrong, so what gives?

308 Win
46.3 grains of 2520
BC is .447
2150 ft altitude
88 degrees F
65% Humidity
velocity was verified with 10 shots thru chronograph, max deviation was 16 FPS

Any help would be appreciated....

 

[fredhorace77]

could be your site height for the scope is off figure or the barometric pressure...also line of site and altitude...all these can make a difference
also drag function...basically i just looked at jbm calculator and tried to figure out what items you might be leaving out or items that you might be leaving as a default setting

 

[necchi]

Try a little experiment.
Run your program with a 200yrd zero.
Then adjust your scope and group to shoot the proper amount high at 100.

 

[tunered]

Headwind ????????

 

[fr3db3ar]

What scope are you running? 5.5 is way out of line for 100 to 200. I'm running 175s out of a 16" barrel 2425 fps and the drop is only 3.6". 150's 2650 fps = 2.6"

 

[lpreddick]

fredhorace77 may be right on. "sight height" on the old hornady ballistic calculator was set at 1.5 in and i didn't notice. ran a lot of ballistic tables and had no problem at short range varmint hunting until i started hitting way high at long range. finally understood what "sight height" was and measured mine and BINGO...mine was 2.5 in and when entered into the hornady program...out came the results. i was one min too high at 500yds...5 in over! this one measurement has the greatest effect on their ballistic table than variations in temp or barometric pressure. a bad scope has also been a problem. keep looking, you'll find the problem.