View Single Post
Old 13th September 2011, 11:32 PM
greyskullnz greyskullnz is offline
Account Deleted
Join Date: Aug 2009
Location: Wanganui NZ
Posts: 268

Originally Posted by Gibbs View Post
Just to clarify my point,
I don't imagine for one minute that you can turn any gun's power down in the middle of a comp!
And I know that thinner air doesn't affect the power of a PCP.

IF, you know you will be shooting in air thin enough to flatten your trajectory, then it could be sorted BEFORE the comp, as I mentioned earlier.

IF however, the air density chops and changes between lanes!? Then I don't know how you would know the change had occured or how you would adjust to it.


I wasn't being flippant, I too would dearly love to have a solution.

Its something that becomes very apparent at Worlds matches, simply because its a different place, different altitude, different weather pattern. Hungary excluded, as that was a very stable climate at a relatively low altitude.

Local shooting can vary a bit between one end of a country and the other. Those who travel a bit would notice a small change every now and then, and perhaps use Summer and Winter settings, perhaps no more than 8 clicks difference. (similar here)

But every now and then I encounter a match where the temperature soars very high, or stays very low throughout the match at low altitude. Same head scratching goes on along the firing line. I just document it and try to learn from it.

As I see the problem currently, the zero of an air rifle changes up or down depending on the CHANGE to the Density of air, not just the zero but also the trajectory past zero by a larger magnitude. I prefer to work in Density Altitude as I can "hang a handle" on the quantity of change, and someone else has done the work of doumenting how to work it out. No need for a computer to do that, it can be done manually on the firing line in about 5 seconds if you have a temperature guage with you, and a DA chart.

What is still puzzling me, is the actual amount of shift up above zero, and the amount of shift below zero, which occurs with a change in DA. For example: how much change above zero is 1500ft DA worth, and how does that affect the trajectory past zero once you have reset it. If you reset your zero before a match, your trajectory past zero is then an unknown until you totally reshoot and relearn your entire trajectory. I'm basically looking for patterns from real results, and then I'll address the maths.

I think we can develop a simple system to leave zero alone, know it is so many clicks high or low, and know how the entire trajectory is the exact click. This all done; knowing how things react to a quantifiable change in DA, and knowing our rifles.

How to manage that is the challenge on the firing line. I'm hoping I am making progress with some solid data starting to yield a few clues. Bit early to make a solid statement, but I am happy its showing a predictable pattern and a way to counter it reliably.


Last edited by greyskullnz; 13th September 2011 at 11:38 PM.
Reply With Quote