Re: tank gun acceleration versus orbital gun acceleration

I've been wondering about the acceleration that's placed on a projectile
fired from a modern high velocity tank gun, versus the acceleration
that's
placed on a projectile fired from one of those theoretical superguns
 
The velocity would be lower on a theoretical supergun for a few very
basic reasons. As I learned in the Field Artillery school the big one 
is gravity, all things will fall unless enough propellant is placed
behind it
and it is given the proper quadrant (up or down) to reach escape 
velocity or level flight

Tank Guns and in particular modern smooth bore tank guns are designed 
to be fired in an almost a flat trajectory Although this by  the laws of
ballistics
is impossible, that is always the goal so as to eliminate as much dead
space
( the area between where the projectile starts to clime and it falls to
hit the point of aim) as can be done, there by extending the kill zone.
The higher the
velocity the flatter the trajectory.

The next factor to be considered is mass Vs propellant, the heavier the
object to be launched the more propellant is needed to reach escape 
velocity. This would restrict it to a supergun as the size and weight of
any worthwhile pay load would necessitate a large amount of propellant
and a far heavier gun tube then any tank would like to lug around.

The artillery type supergun would be the way to go, in that they would
be big
enough and strong enough to with stand the blast but at a lower velocity

there by negating the need for super reinforcement for the  satellite.

To point out the feasibility of this we need look no further then the
W.W.I
German Paris gun, it fired a 307lb shell 24 miles up and 92 miles in
range.
If you were to marry this shell up with a RAP (rocket assisted
projectile)
I see now reason why it could not achieve orbit.

 Don