Get Chairgun, its free. www.chairgun.com
To erdept and others. This is how you use the program and what numbers you will need.
MV (Muzzle Velocity):
Mass (Pellet Weight in grains):
BC (Ballistic Coefficient):
I will use erdept's AA S 410 ERB, .22 as an example. This is variations in Inches not Mil-Dot.
1)MV (Muzzle Velocity): This is the Feet Per Second (FPS) that your gun shoots at the end of the barrel. This changes depending on the weight of your pellet, and also the air in your tank if you have a PCP, and also changes if you have a power adjustment wheel or setting. To get the MV use a chronograph at the Muzzle (The end of the barrel). If you dont have one then you can first check www.straightshooters.com and see if they have your gun. If they do then click on your gun, and click on the link "Our Take." Then click the link "Velocity Test Results." They will tell you the FPS using your gun with different pellets. Here is the page for your gun: http://www.straightshooters.com/ourtake/ottestaa410erb.html
Since you didnt say what Pellet you are using I will use the JSB Exact in .22 to get your FPS. Which they have listed as 927fps
2)Mass (Pellet Weight in Grains): Chairgun lists the pellet weights of just about any pellet you can buy. You get the data by clicking the "Pellet 1" button under the Variable Data Screen. Also the straight shooters website also shows pellet weights. If you want more accuracy than that you can buy a reloading, jewlers, diamond, or powder scale to weigh your pellet. Even better if you weigh the pellet then shoot it through a chrony. For the JSB Straight Shooters said 15.8gn
3)BC (Ballistic Coefficient): This is how aerodynamic your pellet is. Basically how well it flys through the air. Think about throwing a wiffle ball, versus throwing the same ball without the holes. They would be roughly the same weight but the wiffle ball isnt "aerodynamic" so it doesnt go as far. Same thing with pellets. 2 pellets can leave the gun at the same speed (FPS), but if one has a higher BC then it will go father than the one with a low BC. To get an accurate BC you need to use a chrony at the end of the barrel, and then another chrony closer to the target to check the FPS from a distance. This requires alot of equipment so we can just take the numbers from Chairgun or straight shooters using the same method as finding the mass. Straightshooters says the BC is .026
4)Scope Height: This is how high the scope is mounted on top of your barrel. 0 Scope Height would be if the scope was inside your barrel. There are many ways to figure this out. Here is one method to get precise: http://www.network54.com/Forum/79537/message/1191092281/Here%27s+a+different+way+to+directly+measure+Sight+Height+of+a+riflescope
You could also get a ruler and measure from the middle of the barrel to the middle of the scope for a very rough quick figure. In general with medium rings the scope height is 1.5" which means your scope is mounter 1.5 inches above the barrel. We will assume yours is 1.5" for the example
5)Zero: The yardage at which the bullet hits exactly where the crosshairs meet. In your case you have made it zero at 25yards. Enter 25 under Zero in Chairgun
Thats all chairgun needs: Click the graph button. Then Select Ballistic Table under Tables. It will produce a ballistic table with some great data. Pay attention to POI (Point of Impact). This is how many inches up or down your shot will be at various yardages if you aim in the center of the cross hairs. So here is a few yardages for you:
Remember: If any of the 5 things change or are not as I stated then your POI (Point of Impact) will change.
Mil-dots: Chairgun will also let you calculate MilDot's POI's instead of Inch POI's. BUT the key here is you have to tell the program what zoom magnification you are using. 1 Mil-Dot at 5 zoom is a lot more inches than 1 mil-dot at 15 zoom. I personally have 5-15x zoom scope. So I put in a zoom of 5. Then when you look at the balistic table there is a column for mil-dots that will tell you the hold over. Then if I decide to shoot a target at 10zoom then i merely double the amount on the chart. If I'm at 15zoom i triple the amount on the chart. Find what works for you. if you have a 3-9 scope. Chart it on 3zoom, then you have a good way to double or triple the number.
Optimum Zero: If you want to find this like I posted on my last post, then click the Killzone button in Chairgun. It calculates the best zero distance for you based on your gun and your pellets data. The mission here is to find a range where your point of impact doesnt change much over a long set of distances so you dont have to aim above or below the target too much. You set the distance (Kill Zone) that you would like to be the maxiumum you would like to be off by, then it calculates the distance you should zero at. As Easy as that.
Ill try to write this in its own post in the future with some more steps for reference.
Adrian AKA laanguiano