GDG- Ranging, Trajectories, and Sights

[Batrinque at aol.com]

In a message dated 10/23/06 8:34:12 PM Pacific Daylight Time, jspragg at iw.net 
writes:

> The cylindro-conoidal hollowbase projectile fired from the rifle-musket 
> had a lower muzzle velocity (960 ft/sec?) than the round (spherical) 
> ball fired from a smoothbore (some loads as high as 1500 ft/sec).  But 
> the round ball has such a miserable aerodynamic shape that it shed 
> velocity at a greater rate, diminishing its speed advantage that much 
> more quickly, rendering it less effective, and giving it a very steeply 
> curved trajectory of its own -- even if the smoothbore/round ball 
> combination had not grouped so poorly as to cut hit probability below 50 
> percent at ranges of 80 yards or so.
> 
> Therefore, despite following a highly arched trajectory by modern 
> standards, the rifle-musket/Minie' bullet combination represented a 
> major leap in effectiveness over any smoothbore in terms of effective range.
> 

Actually, I don't think the data quite supports this picture (and a number of 
military writers of the era expessed a preference for smoothbores over rifle 
muskets because of the smoothbores' flatter trajectory).  As best as I can 
make out, exmining the ordnance test data, the round balls shot from smoothbores 
declerated at approximately 60 feet per second per second, while the 
rifle-musket Minie bullets declerated at about half that rate.  Thus, it actually took 
a loooong time for the smoothbore round ball to slow down to the same speed as 
a Minie ball.  Where the lousy aerodynamics of the smoothbore round ball 
actually comes into play is when looking at the fine details of the trajectory.  
The forces exerted on a nonrotating sphere would push it unpredictably to the 
right or to the left or even up or down; a smoothbore musket with the same load 
aiming at precisely the same point could not expect two rounds to hit in the 
same spot with any confidence.  The rotating MInie ball, on the other hand, 
balanced those forces out, so that much greater precision of repeatability was 
obtained.  The longer ranges expected from rifle-muskets was not due to greater 
velocity but from greater precision of trajectory.

Bruce Trinque
Amston, CT