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Why and why not to shoot long distance subsonic
Here's a comparison of three rifles and cartridges shooting the same 220 grain Sierra Matchkings at 1000 yards.
The first is a 30" barrel 300 Remington Ultra, The second a 24" 30-06 and the third a 16" 300-221 loaded subsonic. The others are loaded for about 90% of SAAMI max presssure.
The listed values are:
MV = Muzzle Velocity fps
ME = Muzzle Energy ft-lbs
TV= velocity at 1000 yards fps
TE = energy at 1000 yards ft-lbs
%E = percentage of original muzzle energy remaining at the target
TF = Time of flight in seconds
DM drop from 100 yard zero minutes of arc
WM wind drift for 10mph crosswind in minutes of arc
Cartridge MV.. ME TV TE %E TF DM WMOA
300Rum 3000 4795 1811 1747 36 1.29 22.4 4.82
30-06 .. 2500 3330 1440 1105 33 1.58 34.4 6.45
300-221 1000 533 795 336 42 3.40 178.6 6.68
The numbers speak for themselvs. The only thing most people find surprising is that the subsonic wind deflection is very reasonable. Drop due to gravity is predictable but is very sensitive to time of flight which is dependent on muzzle velocity. Velocity deviation is the the most important factor in loading subsoinc ammo for long range. Benchrest loading techniques are necessary or vertical stringing will kill accuracy. A laser rangefinder and target knobs are a necessity too. Drop increases exactly with the square of the time of flight.
Last edited by LouBoyd; 08-16-2008 at 01:53 PM.
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Dude, ROTFLMAO!
LOL yeah, but it was fun!!
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