Hi MS
Good question !
I am cribbing my answers from a number of sources, including Jesters config summary and the cfgWeapons summary from the commented config (both attached in a zip).
Since the Ammo and Weapon configs are designed to handle everything from flashlights to flamethrowers there are a lot of entries that are either redundant or irrelevant to plain old vanilla bullets.
For example - in the default Ammo config there are entries for thrust, thrustTime, maxSpeed and initTime. It looks as if these are designed principally for missiles and rockets.
For example - if I made an Ammo type with initTime of 1, initSpeed of 0, thrust of 1000, thrustTime of 10 and maxSpeed of 1000 then this thing would (should ?) start with zero speed, wait for 1 second, then accelerate by 1000 metres per second per second to a speed of 1000 m/s then stay there for 10 seconds.
If I fired this thing on a flat plain exactly along the horizontal then gravity should pull this thing to earth within the first half second or so. But if I fired this thing with some upwards angle then the upwards portion of the thrust vector should counteract gravity, at least for 10 seconds.
Now go and try to get your bullet into orbit ! ;D
Back to your weapon. My guess is that if you set the Ammo config maxSpeed to 9999 and ignore the thrust and initTime values (so they default to zero) then that should make your weapon start at 9999 m/s(initSpeed), with a maximum speed of 9999 (maxSpeed). Gravity and friction will start to take over, but for any target up to about 1000m this should have no noticable effect.
Result ? Flat trajectory, as required ! ;D
Good luck !
Roni