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1/25/2018 7:38:29 AM
Posted: 5/27/2003 9:52:29 AM EST
I was looking at the ballistic charts for the .22LR ammo that I usually shoot.

It is American Eagle copper plated hollowpoints. Part# AE22.

You can find the ballistic chart at www.federalcartridge.com and following the links.

Anyways, one section of the ballistic chart says if you Zero your rifle at 50 yards, at 100 yards the bullet will be -6.3" below the line of sight. So far so good.

Then on the other side of the chart, it says if you zero your rifle for 100 yards, the bullet will be +2.7" at 50 yards.

What's going on here? On the second chart, shouldn't the POI be +6.3" @ 50 yards with a 100-yard zero?

Also, won't these values change with different barrel lengths? How can I put any faith in the numbers if they don't tell me what barrel length they used for their tests?

As you can probably tell, this is my first time really reading a ballistic chart and trying to figure out what it all means.

Thanks for any help.

-Nick Viejo.
Link Posted: 5/27/2003 2:12:57 PM EST
The chart is correct. It's hard to explain, and I don't fully understand it myself. Basically, a bullet starts to climb after exiting the muzzle for a distance then gravity pulls it down until it finally hits the earth (picture a rainbow). Due to this curvature of the bullets trajectory, raising the point of impact (POI) at 100 yards doesn't mean an equal rise at 50 yards. Also the height the scope sits above the boreline affects this as well, but I definitely don't want to strain my brain trying to figure that into the equation. If I remember correctly, the POI of a .22LR is the same at 25 yards and 100 yards (with it high in between).

You would also think that a rifle sighted-in at 25 yards would shoot low at 100 yards, but it doesn't always work that way either. I helped a friend sight-in his new .17 HMR the other day. We sighted the scope in at 25 yards first to "get on paper" at 100 yards. After sighting-in right in the bullseye at 25 yards, guess where the bullets impacted at 100 yards? 3.5" high!

All in all, it's pretty confusing. I just trust the charts. I believe that most use a 24" barrel and a scope mounted 1.5" above the boreline for ballistics tests.
Link Posted: 5/27/2003 4:37:09 PM EST
Link Posted: 5/27/2003 5:35:35 PM EST
[Last Edit: 5/27/2003 5:37:37 PM EST by AeroE]
Part of your question is about barrel length - the difference will be unnoticeable. Also remember that the best use for ballistics tables is to get your first few shots on paper, followed by fine tuning of the sights, which accounts for your rifle, shooting style, and so on. Never rely on ballstics tables to provide an absolute figure for an exact zero, there are too many estimates for bullet drag and so on for them to apply absolutely or universally.

Try the online program at www.norma.cc; this will show you a graphic reprensentation of your trajectory. [You will need to supply a bullet weight and ballistic coefficient.]
Link Posted: 5/28/2003 5:07:46 AM EST
The deviance of the bullet rise at 50 yards is NOT going to be the same as at 100 yards. Just like the drop is not going to be the same at 200 yards as the drop at 100 yards.

Remember that the downward pull of gravity causes the bullet to ACCELERATE downward. I.E., the further it travels, the FASTER it drops.

A bullet's ballistics are not linear, it does not travel in a straight line, and the arc of the bullet's travel is not the same from 0-50 yards as it is from 50-100 yards, etc etc...
Link Posted: 5/28/2003 7:26:16 AM EST
Correct.. and also there is a drag component...

The bullet is slowing down in forward speed as it accelerates downward.

This is all first year calculus.

Also, a bullet does not just "rise" from the muzzle...

The scope or sights actually look down... the bore is angled up in relation to the line of sight. The projectile is launched at a slight upward angle.

The charts are accurate, but you can also interpolate in between plotted points.
Link Posted: 5/28/2003 7:43:31 AM EST
A bullet will spend a relatively long time near the top of it's arc. That happens before the 100 yard mark if you zero at 100.

Once a bullet is at the top of the arc, it accelerates downward, so the path variation from the line of sight will be the least while the bullet is near this point. At 500 yds, the bullet will be dropping like a rock.
Link Posted: 5/29/2003 4:08:48 PM EST
Every one is correct, review a graph.

Gravity will pull the bullet toward the ground at the same rate of elapsed time regardless of its angle of flight.

As stated, the line of sight is a straight line; the flight of your projectile is not.

Through a rock at a pop can set at 15 yards distance...get it?
Link Posted: 5/29/2003 7:22:54 PM EST

Basically, a bullet starts to climb after exiting the muzzle for a distance

Bullets do not climb after leaving the muzzle in the true sense. The barrel is pointed slightly upward in order to cross zero at the distance it is sighted in for.

If you fired a rifle with the bore dead level, the bullet would start dropping immediately after leaving the muzzle.
Link Posted: 5/30/2003 12:51:13 PM EST
Think about the arc a Quarterback has to put on a "hail mary" throw. He throws it 'up' so that as it travels downfield gravity eventually pulls it back down to where the receiver can catch it.

The barrel of your rifle must also be pointed (slightly) up because, alas, bullet must also follow the laws of gravity.

Gravity - its not just a good idea, ITS THE LAW.
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