Somebody please explain this bullet drop.

[Destructo6]

It would seem that the muzzle velocity is not exactly what the ammo says on the box.

It sounds like you have all the other factors figured out (sight height, zero range, bullet weight, etc) and they are easily measured either by ruler or by mfg statement.

One variable is obviously not right and I'll guess that it's honest to God muzzle velocity.

 

[tomcatt51]

Most .22lr powder is done burning in a 16in barrel.

To experience an 8in drop at 100yds vs 3in would be the equivelant of that 36gr bullet with a rated muzzle velocity of 1260fps somehow falling to a muzzle velocity of under 1000fps. I seriously doubt that's happening.

Actually 16" is the point of diminishing returns in a semi-auto 22LR because that's where the bullet is when barrel pressure is low enough for bolt opening to start and that bleeds off the pressure in the barrel. I have an old model 69 Winchester (bolt action 22LR) that had a 26" barrel I shortened to 20" and lost velocity, and it got a LOT louder...

As to the bullet drop you need to know the bullet velocity, accurately measure the sight height and then carefully sight in based on your group center.

One thing I see is that the OP's 25 yd group is low. That really throws things off farther out. What I'd suggest is sighting in 1" high at 50 yds (one of the table distances and heights) so the group CENTER is 1" high,and see where the 100 yd groups are then.

OR, sight in 3" low at 100 yds and see where your closer up groups are. The farther out you sight in the less error you should have.

Just my 2 cents...

 

[bamashooter]

I'm surprised this got to post #13 before someone mentioned barrel length when talking about bullet drop!

You also need to chronograph YOUR ammo coming out of YOUR gun in order for the info from a ballistic program to be worth anything - SISO principle!

Not my experience at all with multiple calibers and weapons. Input the basic data fields and I find the calculators to be very close. 100 meters and in.

 

[Blackstuff]

Not my experience at all with multiple calibers and weapons. Input the basic data fields and I find the calculators to be very close. 100 meters and in.

Well that likely means you're using ammo consistent with the claims on the box and a gun close to the gun parameters the ballistic program was designed around! It also depends on a persons definition of the word 'close'.

 

[Engineer1911]

More confusion

The rifle is a Ruger 10-22 (custom built match gun) with a Simmons 6.5 x 20 x 50 MM (MidwayUSA $125) mil dot reticle scope. At 14X the crosshair is a 50 yard ZERO, 1 dot above the cross hair is a 25 yard Zero, 1 dot below the cross hair is a 75 yard zero, and 2 dots below is a 100 yard zero.

My target was a 11 meter air rifle target with 11 bullseyes on it. The range distances were measured, ammo was CCI HP MiniMags.

I tried other scope magnifications; 10X, 12X, 15X, and 20X; but had significant deviation from a "zero setting" . The 25 and 50 yard groups were one-hole 5/16" centered where the X-ring used to be. The 75 yard group was 1/2" centered in the black. At a 100 yards all the shots were in the black bullseye.

I have two M41 S&W target pistols with red dot sights, a CMore and UltraDot. At 75 and 100 yards, bullet drop is about 4" and 10"+ . Because of Dot size vs. Bullseye diameter, group sizes opened up to 3" and 5". My conclusion was that you can't shoot a small group if your dot is bigger than the target.

This is not an apples to apples comparison, but I believe it helps understand the difference between dot sights and scopes.

 

[bamashooter]

Well that likely means you're using ammo consistent with the claims on the box and a gun close to the gun parameters the ballistic program was designed around! It also depends on a persons definition of the word 'close'.

My "close" is within 2" at 100 meters with a 22 rifle, closer with an AR and much closer with lesser distant targets. Basic box ammunition of varying grains and bullet types. At a 100 and greater I typically use a LPV scope. I use calculators to get me within 4-5 inches at distances greater than 50 meters followed by an adjustment or two for elevation. Regarding calculator data, my normal input is pretty generic Normally the data is within 2" / occasionally 3" at 50. Side note: Not long ago I tried the 50 zero at 10 (AR) and was really surprised how close it was. All of my zeroing / testing is conducted using a single sandbag up front while sitting at an old government metal table. I would someday like to have a calculator which incorporates barrel length and other variables (if they exist) not typically found with online calculators. Don't know if I could do much better than I do now but it would be interesting to see if I could out perform myself with additional data while being limited to off the shelf ammunition.