61 yards my longest shot

[BilletHead]

11 minutes ago, fishinwrench said:

If you'll give me the following info I'll get you a ballistic calculation.   I need to know the following...

Scope height: measure from center of bore to center of scope barrel.

Range you are sighted in at.

How far low your POI is at any range beyond your sight-in distance. (Just get me a figure within 3/10 of an inch).

The exact pellet (brand/type) you are shooting, and it's weight in grains.

If I have that info accurately added into Chairgun I can calculate your velocity,  ft/lbs of energy, and can also pull up downrange ballistics.   

          I  will get you that info as close as I can when it warms a bit. From my Uncles toys I have info from his crony up close. 

BiletHead

[fishinwrench]

1 hour ago, BilletHead said:

          I  will get you that info as close as I can when it warms a bit. From my Uncles toys I have info from his crony up close. 

BiletHead

Actually if you enter the data from a crony your ballistics won't be accurate in the real world.  You gotta build it backwards.  

I don't know why, but that's just the way it is.  Cronographs are only good for comparing after modifications, they are worthless for determining real world velocity and using THAT info to form a ballistic chart.  It will be wrong every time.  The BC (ballistic coefficient) is never factored in, and is ever changing, so to get honest real world data that you can depend on, you have to do it a different way.

[fshndoug]

pretty technical for popping tree rats boys.I bet it is fun though.I used to shoot  them with a .22 ruger with cci minimags.Shot a fox squirrel so far up in a sycamore once that by the time it .hit the ground it was a gray.

 

[Basfis]

On 12/29/2018 at 3:14 PM, fishinwrench said:

Actually if you enter the data from a crony your ballistics won't be accurate in the real world.  You gotta build it backwards.  

I don't know why, but that's just the way it is.  Cronographs are only good for comparing after modifications, they are worthless for determining real world velocity and using THAT info to form a ballistic chart.  It will be wrong every time.  The BC (ballistic coefficient) is never factored in, and is ever changing, so to get honest real world data that you can depend on, you have to do it a different way.

Physics apply differently to an air gun than a center fire projectile? 

[fishinwrench]

1 hour ago, Basfis said:

Physics apply differently to an air gun than a center fire projectile? 

Nope.   But accuracy in the ballistic data matters more.   Lots of "fudge room" in the world of center-fire ballistics.   Next to none in the sub-sonic airgun world.

Chronographs are junk science.  Shoot through 20 different chronys and you'll get 20 different readings.  Using the same one however can be useful comparing loads and stuff like that.  But in the airgun ballistics world 40-60 fps is a significant thing.

[nomolites]

Same with bows/arrows.  Making mathematical projections using data from actual performance is the only way to set up a reliable sighting system.  That makes all another variables like anchor points, etc. non issues.  Reliable means you can quickly acquire the target and shoot, HITTING your mark - for me a bazillion hash marks or sight pins results in indecision and misses. K.I.S.S. 

Mike