Question about Bushnell Trophy 3-9x40 Rifle Scope, Matte Finish Rifle Scopes
Need manual for scope adjustment , so I don't have to waste ammo
There is no manual for elevation and windage adjustments. (at least not one that comes with your scope; all your scopes manual will say is whether its FFP or SFP (First Focal Plane or Second Focal Plane, the scale used on your scope for mil dots)(you can get this info by finding a store that sells this scope and asking a sales rep)
To adjust for elevation and windage you have to take into account the daily factors (unless your shooting in the same indoor environmental controlled shooting range each day you SNOB! jk
The formula takes alot of variables into account and is known as Exterior Ballistics
!) Environmental Factors - First thing you account for.
A) Elevation from sea level plays a large part into your environmental adjustments. Your elevation from sea level determines largely the Barometirc Pressure but it also varies slightly with Temp and Humidity (Major Factor)
B) Temperature - The temperature can affect the density of the air. The hotter it is the thinner it is and therefore less resistance and a higher bullet trajectory (Minor Factor)
C) Humidity - This again will affect the densify of the air infront of your bullet (Minor Factor)
D) Barometric Pressure - The other large factor in air density this is the base stat that the others modify
These all combined create a ratio that you apply to standard MOA (windage and elevation adjustments) to obtain the shooting information for that particular environment)
2) Bullet Factors (Listed on the Box you buy) - There are a few bullet factors to take into account.
A) Speed - the bullets feet per second can vary as much or more than 500 feet per second with the
same caliber ammunition.
B) Grain - The Grain of an ammunition is a measure fo its "Sectional Density" or weight to volume
C) Ballistic Co Efficient - This number is the measure of the bullets ability to maintain its speed
during flight. This also varies from Grain to Grain
These factors are complex and a pain for the best of shooters to determine. adding to that confusion. there are many ways to determine a bullets ballistics coefficient and each one gets a different number. In this case bullet data is best retieved from the manufactuerers box and take their word for it.
3) Lastly you account for shot factors.
A) Range - by referencing your standard elevation MOA adjustments and mutliplying by the ratio for environment the Elevation MOA is achieved.
B) Windage - Windage is done in inches per mile per hour then is multiplied by the Mph of the wind.
In order to be precise the windage is done in inches instead of MOA. it needs to be converted heres and example.
You Ballistics Cheat Sheet for the day says the windage at 900 yards is 5.2 Inches per mph of wind.
you apply the ratio for your environment .90 (all example numbers. this number would represent a shooting environment with an air density lower than standard/ the cheat sheet's known MOA adjustments). the 5.2 inches is multiplied by .9to acheive 4.68?? idk the point is you mulitply that by the wind of 10 mph to achieve a total of 46.8" of wind drift to the target.
now for the conversion to MOA. 1 MOA is eqaul to 1.047" per 100 yards. meaning for every 1 moa you adjust the bullet will move 1.047" per 100 yards (our target is 900 yards; meaning that each MOA for this target is 9*1.047" = 9.423" per MOA adjustment. so take that number and divide our total wind drift by it. ie 46.8 / 9.423 = MOA Windage Change of 4.9665... now you need to know whethere your scope is 1/4 minute clicks or 1/8 minutes (how many spaces between large numbers?) you would adjust to 5 MOA for a 1/4 minutes scope equaling 20 clicks on an 1/8th minute scope it would be 40 clicks.
This is the math of shooting. to learn how go to
WWW.shooterready.com they are an excellent sight to get the math down WITHOUT wasting ammo. Once you have the math you an transfer it to your gun. waste a few rounds checking it out and youll be hitting targets @ 1800 yards in no time
I like to take the simple way after i learned how to do the hard way
There is software tha will do the exterior calcualtions for you.
if your interested i use Sierra Infinity V6 Ballistics Software
Posted on Apr 08, 2009
I have the same scope, but I don't have the manual. If you are shooting a bolt action, take out the bolt, rest the rifle in a cardboard box, sighting down the bore at the target, put the crosshairs on the same target without moving the gun, it will hit its mark at 100 yrds.
Posted on Dec 10, 2008
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