Ballistic Puzzle: POI vs Velocity and weight.

[xp220]

This may have been discussed before, but i could not find any satisfying answer when I searched web, especially for my case. I hope that some experts in NES could help.

I have zero-ed in my CZ452 (16" barrel) to 50 yd with CCI Velocitor (40Gr, 1435 ft/s, HP). When I shot another ammo, CCI Mini Mag HP (36Gr, 1260 ft/s, HP), the POI is consistently ~1 inch higher and ~0.5 inch to the left.

From basic physics of trajectory, I would assume the Mini Mag HP should hit lower than the Velocitor since it has lower speed. There many "explanations" about the effect of recoil of slow bullet on the web, but there similar amount of rejection of that theory. Does BC play any role here?

Is there any web site that I could do some simulations of different factors to explain what I saw?

 

[jar]

http://www.rifle-accuracy.com/harmonics.htm has a possible explanation.

 

[bpm990d]

BC of the projectile will always play a role, but the question is how much. The correct drag function is the RA4 for .22LR, but it is esentially the G1 drag function below 1400 fps.

The link below gives G1 BCs for a variety of .22lr bullets that came from Bob McCoy's BRL report that was published in 1990.

http://www.exteriorballistics.com/ebexplained/22rimfire.cfm

You can get a free ballistics program at Berger Bullets and then run the numbers. Because it's a simulation involving a comparison between two loads, you will have to select an arbitrary zero range (like a 100 yards) and then look at the trajectory at 50 yards. If you select 50 yards, the program will just show "0" at the 50 yard and you wont be able to compare the trajectory.

It's probably a combination of a variety of things, but unless you know the exact velocity (with a chronograph) and BC of those specific projectiles it's really just a guess.

Let us know what you find out.

B