I did not mean buy a gun Don but more the idea behind it. A tube for the projectile and a gas-tight chamber which you could pressurise with a bicycle pump through a non return valve (bicycle valve) and an accurate pressure gauge and a trigger or release mechanism. Or maybe one of those gas cylinders you can buy to make fizzy drinks to prime the cylinder. The thing is you could alter the pressure and so the velocity easily and over the short range you have that would not alter the trajectory significantly. Just happy thoughts to help keep you from getting bored!
