Air Gun Home :: View topic - Trajectory Calculator

shawnhu · Member

Does anyone know where I can find the formulas for calculating trajectory in Excel?

I know of some websites that would do the calculations for you, but was curious to know if there are any Excel sheets out there.

I'm looking to plot a few different senarios and print them out to study or create a cheat sheet.

SMP · Silver Status Member

http://www.hawkeoptics.com/apps/chairgun-pro.html

Download this for free. Simply awesome software

Dukemeister · Member

Chairgun is great!
If you do want to do your own tweaks in EXCEL, try this site:
http://www.jacksonrifles.com/ballistics.htm

NZ Shooter · Suspended

The best 'trajectory calculator' is out at the rifle-range. Putting in serious trigger time is way better than any computer programme. I will admit from my limited experience with trajectory software, it can be freakishly accurate - to a degree. There are so many variables that real-world shooting is, IMHO, the best measure of any given rifle/velocity/pellet combination. I pinned a rabbit at 127 metres - on the 3rd attempt. I'd never shot past 80 odd metres prior, and I'll be dammed if I could have done any better having 'chairgunned' the potential situation prior to seeing the bunny. And yes, that was with my Patriot (as seen in my signature). I will admit that I could see where the slugs hit on the first two shots, as the mental bunny decided to keep nibbling on the grass, as
2 15.43 grainers blew up a dust cloud right above him, on a rocky hill - twice. I'm not knocking the use of such software, however I do know trigger time is a great way too know exactly what your gun can do at range. Cool

rsterne · Moderator

The problem with trying to fine tune a calculator to be better than ChairGun is that the BCs are not a constant, they vary with velocity.... Unless you know the BC for your gun, at every velocity between the muzzle and the target.... you can't do a "perfect" calculation....

Bob

twalter · Veteran Member

rsterne · Moderator

Shooting at up or down angles is really very simple.... the drop is relative to the horizontal distance to the target, not the straight line distance.... If you shoot straight up and the pellet crosses the line of sight at 10 yards from the muzzle, then after that it gets increasingly higher above the line of sight and never drops below it.... The rule of thumb is 20-20.... If you are within 20 yards and 20 degrees of horizontal, no correction necessary.... After that, your POI will be above where you expect, whether you are shooting uphill or downhill makes no diffference.... If you are shooting at 60 degrees (up or down), the horizontal distance is half the straight line distance.... If you are shooting at 30 yards (straight line) then use the POI for 15 yards....

Bob

shawnhu · Member

I think the calculations is much more complicated than the horizontal distance, especially since we need to look into flight time. Gravity acts on a pellet as soon as it leaves the barrel, until it hits the POI.

rsterne · Moderator

If you don't want to take my word for it, I suggest you Google it and start reading....

http://www.chuckhawks.com/shooting_uphill.htm

http://www.loadammo.com/Topics/April04.htm

The bullet DROP relative to the line of bore is the same for the same actual distance and flight time, you are correct.... However, the way you must hold to make the shot is proportional to the cosine of the angle of the line of sight.... That means you hold the same as you would to make a shot with the same Horizontal distance to the target....

Bob