Any owner of pneumatic weapon asks sooner or later a question what its actual power. An optimum indicator of power of weapon is the bullet speed measured by means of the special tool – a chronograph. However this device is not always available, and in addition has errors at measurement. Fortunately, there is more available and exact method of measurement of speed of a bullet – the ballistic pendulum.
Instruction
1. To measure bullet speed by means of the ballistic pendulum, make at first its suspension. It can be made of any material in which there can be a bullet. For example, you can take a box about 5х5 centimeters and fill it with plasticine, having added a little lead, or to take bar from metal or a tree and to make in its face dredging for a plasticine layer. The suspension has to weigh not less than 100 grams, but no more than 300 grams. It is obligatory how it is possible more precisely, measure suspension weight.
2. Make threads of such length that the distance of at least 180 centimeters from a suspension axis to the suspension center of gravity was provided. You can hang out the pendulum in a doorway so that it reached almost a floor. To eliminate its rotation, suspend bar on four threads.
3. Take a ruler and the runner which will slide along it under the influence of the pendulum. As the runner you can take an empty frame from a matchbox. Calm the pendulum and expose on it a ruler on zero. Rearrange the runner, without bringing on couple of centimeters to the expected value of speed. Check, how easily the pendulum pushes the runner.
4. Determine the mass of a bullet. For this purpose use pharmaceutical scales and weigh groups till 10-20 of bullets, and then calculate average size. Weight has to be calculated to within one cell of gram.
5. Make a "control" shot by a suspension to make sure that the gases expiring at a shot do not influence a pendulum deviation.
6. Make a shot in a pendulum suspension. After a shot determine by the runner with an accuracy of millimeter distance on which the pendulum deviated.
7. Calculate bullet speed on formula V = ((M + m) / m) * S * sqrt (g / L) V - bullet speed, in m / сM - the mass of a suspension, in kgm - the mass of a bullet, in kgg - the acceleration of gravity, (=9.81)L - suspension length, in metrakhs - a pendulum deviation, in meters
8. For achievement of exact result repeat the procedure several times. Also do not forget about safety measures.