muddyboots wrote:hey Randy, it looked like he kept missing...am I mistaken? No sparks or anything but dust flying all over the place...
I'm sure they're just shooting TP ammunition, which isn't going to spark much when it hits. It's the HEI incindiary rounds that make all the flash when they impact.
With respect to the dirt and dust flying up around the target...it looks like a good hit to my eyes.
Remember that the gun is more like a chainsaw than a sniper rifle. The 20mm and 30mm guns on current fighters have a 3-5mil dispersion. That means at 1000' of range from the target, 80% of the bullets will fall within 3-5 feet of the aimpoint. This dispersion is the result of the way the gun is mounted in the jet and the natural vibrations caused by all that machinery rotating around at high RPM.
In the F-15E, we shoot at between 6,000' and 9,000' of slant range. In the A-10, they shoot all the way out to 3 miles (18,000' of SLR).
So, the math says that even a perfectly placed shot will have bullets falling in a 30'-50' circle around the target -- and that's just the natural capability of the gun itself.
If you want to consider the "aiming" aspect of shooting the gun, consider that any slight movement of the stick will result in that aimpoint moving. Just like with a rifle/pistol, pulling back on the trigger means that some force will be exherted on the stick, and thus the flight controls will move a little. Even a little burp of 1/2 degree will mean the aimpoint, 1-3 miles away, moves quite a ways across the ground. The trigger pull is heavy, not unlike the double action trigger pull of a pistol, and means that a bunch of aft force on the stick is required to depress the trigger.
Also, consider that in the 2-3 seconds that the finger is on the trigger, the airplane is in some sort of dive (10 degrees is the lowest, 30 degrees is probably the highest) and accelerating during that timeframe. As the airplane accelerates and the trim remains the same, the airplane wants to subtly climb. That means you have to push forward on the stick slightly to counter that climb.
What the two forces I've just mentioned -- the aft force on the stick from the trigger pull and the forward push on the stick to counter the trim -- combine to result in is a little bobble every time you're shooting the gun. So combine that 30' circle that 80% of all the bullets are hitting in with the naturally shifting aimpoint, and the net result is a bunch of bullets raining down around the intended target as well as on the target itself.