M&P 15-22 with 2moa Holosun red dot and roughly a 25 yard zero.  Federal 36gr copper plated hollow points.  Every ballistic table I've checked, including Federal's own, says on at 25, 1" high at 50, back on around 75, and about 3" low at 100.  My results are way different.  Point of aim was same at every distance.  On at 25 yards, on at 40, 3.5" low at 60, 5" low at 80, 8" low at 100.

How can the ballistics say 1" high at 50yards and I be 3.5" low at 60?  I do realize red dots are not magnified scopes, but I'm still surprised by the difference.

I have a pic of target but I don't know how to post it on here.

Probably because the ar puts the optic further above the bore than most .22's

ETA Thats my guess without thinking about all those numbers. Pretty tired and a little drunk

bullets drop to the ground at the same speed wether they are fired out of a gun or just dropped, which is 9.8m/s squared. drop a bullet and fire one level at the same time, and they hit the dirt at the same time.  you have to make up for that with all sorts of angles and shit.

science!

What if you fired while running on a treadmill?

I did factor that into all the calculators with 2.5" sight height.

what did you put for velocity and were you able to check what you are getting with that round in your gun?

The trajectory normally crosses the line of sight twice, and the high point of the trajectory is called the max ordinate.

There are three ways you could be "on target" at any given range.

You could be on target the first time and the trajectory will rise to the max ordinate, then drop and cross the line of sight again. Like a 25/300 or a 50/200 AR zero.  This is the normal,situation.

You could also have a zero where your point of impact is actually the second time your bullet crosses the line of sight, not the first time. This would be tough to do at normal zero distances because you would need a shallow max ordinate achieved closer than 25 yards.

You could also have a zero where your point of impact is actualy the max ordinate (high point).  After firing your trajectory rises, hits your POA and then drops, hitting the line of sight once, but never actualy crossing it.

Maybe you have that third zero situation?

Science is bullshit.

I learned that in GD.

Easy.  You're not getting the full 1260 fps velocity.  Either the lot of ammo is slow, or it's slow in your gun.  You're getting right under 1000 fps.  Shoot across a chronograph.




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Ballistics Calculator

Load Number:745FF Zero Range:25 yd
Caliber:22 Long Rifle Temperature:70 °F
Bullet Style:Copper Plated HP Wind Speed:0 mph
Bullet Weight:36 gr Altitude:0 feet
Ballistic Coefficient:0.125 Max Range:100 yd
Muzzle Velocity:975 fps  
Sight Height:2.5 in  


Range (yd)Drop (in)Wind Drift (in)Velocity (fps)Energy (ft-lb)
0   -2.5  0.0  975  76
10 -1.2  0.0  961  74
20  -0.3  0.0  948  72
30  0.2  0.0  935  70
40  0.3  0.0  923  68
50  0.0  0.0  911  66
60  -0.7  0.0  899  65
70  -1.8  0.0  889  63
80  -3.3  0.0  878  62
90  -5.4  0.0  868  60
100 -7.9  0.0  858  59

1260fps from the box.  No I don't have a chrono

That does make sense.

yep, that was my thought (and the reason why I asked about where you got that velocity number from).  most likely the test gun was a 24" barrel and the ammo used was probably manufactured to a little more tighter tolerance than their production ammo.  for cheap and/or small caliber ammo this is common.  the only way that they ballistic calculator will be correct is if you know what exactly that ammo does in your gun.  if you get really picky with them you also need to throw in environmental, altitude, and lat/long (for corellas force).

Height of the center of the optic above the bore.  False muzzle velocity.  False BC entered.

Use tables to give you an IDEA as to what it takes, otherwise shoot known distances and build a dope sheet.

How long is your barrel, and what barrel length was used for generating the published muzzle velocity?  If your barrel is substantially different in length, you're going to get a different velocity.  If you get a higher velocity, the bullet drop less at a given distance, and if your MV is lower, it will drop more for that given distance.