Home Forums Hunting & Shooting Ask The Gunwriters .22 LR and windage....can someone 'splain to me why....

high velocity .22 LR bullets apparently have about twice as much drift at longer distances than standard velocity bullets.
This was brought to my attention by an article in Precision Shooting (or The Accurate Rifle??) several months back....Nov or Dec 02??....that mentioned the phenomenon in passing while discussing shooting .22s at 200 yard targets, offhand as I recall.

This has been known for many years. The usual explaination is the dropping of velocity to the speed of sound affects BC. I don't have the details, but if you look at Sierra's list of BC's, you will see that BC changes with velocities. Round nose bullets often gain in BC as they slow down. Apparently this is what happens with .22 LR ammo, particularly as it slows to the speed of sound. E

From the NRA Firearms Fact Book;

"Wind deflection is not proportional to time of flight. Instead, it is propprtional to the amount of delay in flight caused by air resistance."


"This remarkable result is due to the very rapid rate at which air resistance increases with increase in bullet speed in the region near the speed of sound. The 22 rimfires are the only important rifle cartridges that occupy this speed range, and they are the only ones that show more wind deflection as velocity is increased."

This is a very interesting and informative hand book. I`m not sure it is still in print but it`s worth buying if you run across a copy. I don`t remember what mine cost me but it`s a paperback edition and was dirt cheap inre to the information it contains.

" that BC changes with velocities"

I am not really happy with this statement.

As the BC is defined as

sectional density SD / form factor i

with
SD= bullet weight W / D*D (bullet diameter sqared)
and
i being a factor for bullet shape,

there is no room for a change: the BC is a constant of the bullet.

When we find different velocity related BCs for a bullet in Sierra's reloading manual, this is imho a service to the reader: there could be different BC values for barometric pressure, temperature etc. as well.

It is the drag formula which should take care of the influence of speed etc..


Inspired by this topic, I'll reread the article "Why BC is BS" in PS - I think there is much truth in it.

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If you are familiar with eBay: here you can find "NRA Handbook" quite often.

Thanks guys, with your help and upon a bit more research I've got a basic understanding now. Found a table which, while each bullet and velocity is different, indicates that HV .22 will deflect about 37% more at 100 yards than standard vel. Couldn't find a table which went farther out than that, but since actual time of flight vs time of flight in a vacuum is the determining factor, it could well be as much as the 100%(More or less) mentioned in the article at 200 yards.

The article you referred to has been published in PS #7/50, pp. 91


QuickTarget produced this table:

Tabular trajectory data at Std.ICAO Atmosphere
-------------------------------------------------
Gun / Ammunition : 22 lfB
Bullet : Blei RK
Bullet weight : 40 grains or 2,59 grams
Muzzle velocity : 1000 fps
Crosswind speed : 10 Mph
Ballistic Coefficient(s) (G1):
C1=0,140>0 fps;

Optimum trajectory information : Max. point blank range (P)=76 Yds. with a
zero range set to (X)=65 Yds. and max. ordinate above LOS at range (M)=37 Yds.
-------------------------------------------------------------------------------------
Sight-in clicks, 1 click = 0,72 cm/100 m or 0,283 in/100 m
Height of sight above bore axis = 2,54 cm or 1,00 inch
Gun is zeroed-in at 300 yards, by
sighting-in at level firing
-------------------------------------------------------------------------------------
Range / Velocity / Time of Flight / Energy / Path to LOS / Deflection at crosswind of 10 mph (in,MOA)/Total drop / Sight correction for setting new zero range (in,MOA)/ Target lead 33 fps

-------------------------------------------------------------------------------------
�Yards fps s ft.lbs. in. in. MOA in. Clicks MOA yds �
-------------------------------------------------------------------------------------
| 0 1000 0,0000 89 -1,0 0,0 ----- 0,0 ------ ----- 0,00
| 25 966 0,0762 83 +14,7 0,2 0,83 1,1 -226,1 -55,96 0,83
| 50 936 0,1554 78 +28,0 0,9 1,80 4,6 -215,7 -53,40 1,70
| 75 909 0,2366 73 +38,9 2,0 2,61 10,5 -199,6 -49,40 2,59
| 100 884 0,3202 69 +47,1 3,5 3,39 19,0 -181,5 -44,92 3,50
| 125 861 0,4062 66 +52,6 5,5 4,19 30,3 -162,0 -40,09 4,44
| 150 839 0,4947 62 +55,1 7,9 5,01 44,6 -141,4 -34,99 5,41
M 158 832 0,5235 61 +55,3 8,7 5,26 49,8 -134,6 -33,31 5,72
| 175 818 0,5853 59 +54,5 10,6 5,79 61,9 -119,9 -29,69 6,40
| 200 799 0,6778 57 +50,8 13,7 6,54 82,4 -97,8 -24,19 7,41
| 225 780 0,7725 54 +43,8 17,2 7,29 106,2 -74,8 -18,51 8,45
| 250 762 0,8700 51 +33,1 21,1 8,07 133,7 -50,8 -12,56 9,51
| 275 744 0,9700 49 +18,6 25,5 8,86 165,0 -25,8 -6,38 10,61
X 300 728 1,0722 47 +0,2 30,3 9,65 200,1 0,0 0,00 11,73
P 302 726 1,0804 47 -1,4 30,7 9,71 203,1 +2,1 +0,52 11,82
| 325 711 1,1764 45 -22,1 35,4 10,41 239,2 +26,5 +6,56 12,87
| 328 709 1,1890 45 -25,0 36,1 10,51 244,2 +29,7 +7,35 13,00
-------------------------------------------------------------------------------------
M = Peak vs. L.O.S, X = Set Zero, P = Max. Point Blank Range
Elevation above Angle of Site (0,0 deg.) = 1,0668 deg.

It's hard to read: wind deflection at 328 yrds is 36.1 in.

A (theoretical) 2,000 fps muzzle velocity (other variables unchanged) causes a deflection of 50.3 in.
With a BC=0.28, deflection is 18.8 in at 1,000 fps mv, and 23.7 in at 2,000 fps.

Ballistic coefficient is not an absolute, independent value. It's an index of how a specific bullet's flight compares to the much-studied, thoroughly documented flight of a standard artillery test projectile -- usually the G-1 -- and that standard's ballistics tables -- Ingalls' or Siacci's tables, for example. I'm still disappointed from learning, years ago, that the ballistic coefficient is NOT (as I'd so long assumed) an index of how the bullet flies in air in comparison to how it would fly in a vacuum.

� No other projectile flies exactly like the standard test projectile at all points along its flight or at different velocities (so its ballistic coefficient is therefore different at different points and velocities, even when its muzzle velocity is exactly the same as the standard test projectile's muzzle velocity).

� No bullet's ballistic coefficient based on one standard test projectile describes how the bullet flies compared to the way that another standard test projectile flies. IOW, Bullet A's BC relative to the G-1 projectile's down-range behavior doesn't relate its flight to the flight of another tested standard projectile.