FYI Chairgun2 download...

[BumbleShot]

I just spent a little while looking for the Chairgun2 program and found it finally.  So I thought I would post the download site for all in case some don't know where it is.

Chairgun2 computes ideal trajectories and scope sightings for airguns based on pellet weight and airgun velocity.  It's a great place to start sighting in a scope to get 2 zeroes.

http://www.chairgun.com/offset/chairgun2.htm

Enjoy!

[BumbleShot]

This is amazingly interesting software.

When I bought my first 2 spring guns, the R7 177 and the B26 22, I bought them to work at similar ranges since both rifles have very similar velocities, both rifles can be use atsimilar range with the same zero.  I realize now with the use of this cool software, that I was right about the 2 rifles.  The main differences is the energy is almost doubled with the B26 22.

Now I have a B40 177 with a velocity of about 830 with Beeman FTS, and this rifle is completely different ballistically.

I also realized, zeroing the R7 and the B26 at 20 yards is a mistake.  15 yard zero is a complete mistake, since then all other shots at any other range will POI low.  Instead, I should zero the R7 and B26 at either 12 yards and/or ~23 yards.

A world of understanding is opening up.

[BumbleShot]

So I've realized, I need to resight the R7 and B26 at 12 yards to get a second zero at approximately 27 yards. assuming a mean velocity of 640fps for both.

The B40 177, should be zeroed at 15 yards with a second zero at 30 to 35 yards depending upon the pellet.  In this case CPL, JSB and FTS.  Average velocities from the B40 are going to be around 840fps.  At 23 yards I have a hold under of .3 inches.

This stuff is complicated but really interesting.

Sorry if I'm spamming this subject.  It's really cool though.  

[daveshoot]

I agree, it is fascinating and helpful. It goes hand in hand with a chrony, to see what you are really doing with each pellet selection. If you just plugged in the 1000 fps printed on the gun box, you would get a lot different results!

An interesting thing is experimenting with different scope heights and its effect on OZR (optimum zero range).This might be one of those distinctions between powder burners and air guns.I had always heard that with powerful hunting rifles, the lower the scope mount, the better. With air guns, there is less concern for the sharp reverse recoil, and the lower velocities make for a more pronounced trajectory at shorter ranges. When you are optimizing zero for a given kill zone, the higher the scope (up to a point), the greater the dwell time in the kill zone over range. This is helpful with minor range estimation errors in the field.

They didshorten the earlier Optimum Zero function to "OZR" in the menu. I was happy to find it again.

[Graham]

Chairgun 3 is available now!!!

http://www.chairgun.com/

[speedturtle]

thanks Graham!

Speedturtle