Coyotehunter.net

Hey guys,

Have any of you had trouble with calculating your trajectory with a ballistics calculator vs. real world situations? I've had 2 different rifles that do NOT follow the trajectory charts and i'm just puzzled. You know-- enter the BC, fps, bullet weight, your zero range, sight height, etc. and you get a nice little print out of what your bullet is doing at certain ranges? Both my .25-06 and a 7 mag that I owned shoot twice as high at 200 yards than they do at 100. Now let me explain that both rifles are good shooters so its not some crazy fluke, they both print good groups at 200 yards just twice as high as they are at 100. Anyone have and ideas about whats going on here? Its not a bad thing, I just can't figure it out.

.25-06 load is 57 grains RL19 and a 100 grain hornady interlock @ 3350 fps
7 mag shot 66 grains H4831 and 162 grain hornady BTSP @ 3025 fps

theres other factors such as temperature, elevation, bullet type that are not considered in those calculations.

LeviM wrote:theres other factors such as temperature, elevation, bullet type that are not considered in those calculations.

That seems weird because both my .223's and my .22-250 have been pretty close with the same calculator and neither are shooting higher at 200 than they are at 100. In fact, I haven't seen a single chart in my life that shows a rifle hitting higher at 200 than it does at 100. I am definately missing something here with this calculator or my 25 is one of a kind, which I highly doubt.

http://www.handloads.com/calc/

muzzle elevation?

kflan

There is no fluke.

Need one variable: What is your ZERO range per rifle?

Something I don't see noted, and many don't actually know is that the BC listed for bullets is not necessarily the actual BC of your particular bullet. There is a way to figure out the actual BC which involves shooting at set distances (100 and 500yds if I remember correctly), velocity at muzzle and target, drop, etc and calculating it out. I never have done this myself, but the calculators/software I have used have always been close enough for for my needs at the time. I know I have seen a couple different sites with the explanation and calculations, however I don't remember where I saw them.


To add to Levi's list of variables...barometric pressure, humidity and a whole bucket of other things can throw you off. I do think Pilgrim has a point for your issue though. If your zero range is out of whack, your bullet could very well still be climbing after 100 yards.

Not BC or other.

It's a scope/trajectory matter. Need to know Kflan's POI at 100 to explain.

I have yet to see a ballistics calculator print me exactly what my load is doing when all the parameters are punched in.

Some have been closer than others, but none have been "spot on".

I use the calculator to give me a rough idea as to whats going on down range, but I still do a good old fashioned real world check to make sure.

I have a old program from Oehlors that seems to work fine for all of my stuff. Never have any real issues. I just use the bullet profile from there data base, typically they have the model number I am using, velocity and zeroed range and I am set. Art Pejsa has a book out called Modern Practical Ballistics that realy does a good job discussing exterior ballistics and offers up some easy to use formulas in the field to figure bullet drop.