New question based off of old suggestion

[johnnyj]

I have read that it is good to sight in a scope at about 2-3" high at 100 yards, that way you are about on at 200 yards and 6-8" low at 300 yards. This makes sense to me.

Question #1 What difference does the bullet weight make in caliber such as .308.

Question #2 This is why I asked Question #1, I look at the different ballistic charts and they show that a .308 shoots about 12-15" higher at 200 yards than at 100 yards.

I'm cornfused and please remember there is a difference between ignorance and stupidity.

Please help me out or point me in the right direction.

jj

 

[James K]

We often hear about a bullet "rising" when fired. That idea requires a bit of understanding. No bullet can rise above the line of the gun bore; a bullet fired from a gun begins to drop the instant it leaves the barrel.

If the barrel is horizontal, the bullet will describe a curve and hit the ground at some point determined by the power of the gun, shape of bullet, etc. (Time is not a factor; it will hit the ground at the same instant as another bullet dropped from the muzzle at the same time as the fired bullet exits.)

But we don't normally shoot with barrels perfectly horizontal. Instead we install sights and fix them so that they can be set to let the bullet "drop into" the target at some chosen range. If we keep the sights lined up, the more we raise the rear sight, the more we lower the rear of the barrel, thus raising the muzzle, and the farther the gun will shoot.

Since the sights are usually above the bore, a bullet may cross the line of sight twice, once on the way up and once coming down. In sighting in a rifle, we select some range depending on the use to which the rifle will be put, and adjust the signts so that the bullet will strike the aiming point at that range.

The easiest way to envision a bullet trajectory is simply to use a garden hose; the water will describe exactly the same type of arc as a bullet (though of course shorter). If we raise the hose nozzle, we increase the "range" of the water. We can also extend the range by opening the faucet wider and increasing the pressure and power, just like adding powder to a cartridge.

Jim

 

[johnnyj]

Thanks Jim,

that makes more sense to me now, especially how the scope sitting on top of the rifle affects how we "see" the trajectory.

jj