Canadian Airgun Forum

The vacuum tubes on my present computer can't handle downloading something like Chairgun 2 so can some of you gentlemen help me out? What do you need to know in order to determine the yard marker where a pellet will reach it's high point in trajectory? I'm guessing MV, scope height, pellet weight and BC? What else? If I provide the info in a PM, can one of you do the calculations for me?

Determine your:
- bore to scope center to center (measure shroud outside diameter and divide by two/measure the free space between the shroud and scope bottom at the scopes objective/measure the outside diameter of the scope on the objective end and divided by two/then add all the numbers up).
- scope brand and power
- pellet
- velocity

If you can give me the above information I will do the calculations for you.

_________________
Canadian Airgun Field Target Association (CAFTA)

Where or where did Windbag go, where or where could he be?

_________________
Canadian Airgun Field Target Association (CAFTA)

bump

... LOL .... gone to home depot to get a measuring tape ..... LOL ....

Hey CJN, how about some pics with your instructions .... for newbie like me .... Thx.

Just PM'd you back with your zero and clicks.

_________________
Canadian Airgun Field Target Association (CAFTA)

Sorry Sniper...no pictures on file!

It's easy.

With the scope mounted to the gun....

- Take a caliper and measure the outside of your scope objective (large end of scope). Divide that number by two.

- Measure the free space (the area between the bottom of the scope and the top of the barrel.

- Measure the outside of the barrel, and divide that number by two.

Add all the numbers up and you have the distance between your bore center and your scope center approximately.

If this more detailed set of directions makes no sense at all, then I might be able to get a gun, caliper, and camara and try to get pictures for you.

If you don't have a ballistics program, but are able to follow the instructions above, give me your data and I will find your zero as well.

Take care.

_________________
Canadian Airgun Field Target Association (CAFTA)

Hi CJN,

I think I got it ....lol.....
so

1/2A + B + 1/2C

Your math is right on the money.

_________________
Keyrigger
CAFTA Governor

When you are long winded, is that a sign of Wisdom or Old Age?

I think it is important to remember that sometimes the free space under the scopes objective is measured to the receiver. As is with the case with my Pro Sport and Diana, the barrel is concentricly centred within so take half of the diameter of the whole receiver. Is that right CJN?

Although possible, there is a better chance of the barrel in both of those rifles, being mounted nearer the top, rather than dead centre, giving you an incorrect reading. A steel ruler can be used to extend the objective bell of the scope, forward enough to measure to the barrel, and get you the measurements you need.

_________________
Keyrigger
CAFTA Governor

When you are long winded, is that a sign of Wisdom or Old Age?

I can see how all of this works but I guess I'm old school, I just get out with my guns, a tin of pellets and a lot of paper targets and see where the shots are going... then write down the hold over or clicks and I'm there.

_________________
My shooting pix :- http://www.freewebs.com/fthftshootingpix/

http://www.freewebs.com/shootingpix/

http://www.freewebs.com/shootingpix08

Good work Sniper. That's it.

Note: As Windbags comments above regarding what to do when the scope is not over the barrel, but the receiver.

Note 2: and Keyrigger's follow up.

_________________
Canadian Airgun Field Target Association (CAFTA)

That's always the best way. Whether starting with the computer program or not, all confirmation should be on the paper.

I like setting out paper target every 5 yards. Starting at 10 yards and going out to 55.

Ballistic coefficient is the hardest factor to determine when entering information into the ballistic programs.

_________________
Canadian Airgun Field Target Association (CAFTA)

Good idea!!

_________________
Canadian Airgun Field Target Association (CAFTA)