Some insight into why what we shoot shoots the way it does..

Strategy, Technique, Stories, etc.
Post Reply
pirellip
Posts: 170
Joined: Thu Jun 28, 2012 10:03 am

Some insight into why what we shoot shoots the way it does..

Post by pirellip » Wed Jun 25, 2014 2:06 am

I feel that I'm giving away some of my *trade secrets* by sharing this, but I know only the 'good ones' read this forum :o

http://www.ctcustomairguns.com/hectors- ... oefficient
Tom
CAFTA Governor

Mac
Site Admin
Posts: 704
Joined: Mon Jun 18, 2012 9:39 pm

Re: Some insight into why what we shoot shoots the way it do

Post by Mac » Wed Jun 25, 2014 12:46 pm

Thanks for the post and link. I read that and it is the second article I have read that refers to varying BCs at different ranges. That is probably why most ballistic software has a weakness at the close, far or both ends of the click chart from 10 to 55 yards.

With the 7.9 JSB at WFTF power levels, I find that most of the time I need fewer clicks from 45 to 55 yards. This would seem to indicate a higher BC at or just before those distances.

Also, when I shoot the heavy pellets from 18 to 20 ft/lb, the chart is much closer to what I find when I actually shoot those distances, which would seem to indicate less variance in BC.

I like the software for getting close, but there is no substitute for actual shooting at all distances. I am trying to do this fairly quickly on the sight-in range before every match and my scores have been improving. Go figure.
Tim
CAFTA Governor

pirellip
Posts: 170
Joined: Thu Jun 28, 2012 10:03 am

Re: Some insight into why what we shoot shoots the way it do

Post by pirellip » Wed Jun 25, 2014 1:04 pm

I paid the $5USD for Hector's software and have found it to be well worth it. His approach is the only one I know of that takes into account shimmed scopes - this is achieved because it uses real world data to obtain the trajectory, so any effects from the scope vs barrel angle are incorporated.

In fact, the PP Calc will not work unless you enter the POI/clicks at 3 ranges (on top of your zero) He suggests using your closest distance, your farthest distance, and the middle point between your zero and farthest distance.

The idea is that once you arrive at the range, you zero your rig, then shoot these 3 distances and record the clicks/change in POI that you find. Plug these 3 into his software and it produces your chart, splitting the BC into 3 sections - near to zero, zero to middle and middle to far.

It's worthy to note that his program isn't just a 'line fitting algorithm' like Eric Saunders' software (which I also like) as with Hector's if you put garbage in, you get garbage out - which is a good indication that something may be wrong with your shooting that day - which can be very common when shooting a piston rig.

As he says, "You can't trick Newtonian Physics" if your POI suddenly take a nose dive from the middle to far section, something is wrong with your rig, or you are 'off' on your shooting technique.
Tom
CAFTA Governor

Post Reply