An odd question though...
Where can i get BB Gun that can fit on my RC Plane.
If i could get one, i will fit them below fuselage or on wings...
Is there any mechanism which works for this!!!  
Seniors, pls enlighten  

Even if you got one (check RC Tank spare parts) it would be useless. One assumes that you would open fire in flight. The wind would sweep the pellets off course.

Sir, pls point the link...

Av..with rubber bullets, i found the speed of the aircraft slows down as it fires continusly.. so, use tracers.. real game.. and need more powerful motors and battery.. was also trying with sound generators.. but at high distances it wont hear or seen.. so, try rockets.. tiny rockets.. from cracker shops..