Gas operated extendible probe for ballistic model

Claim 1

A BALLISTIC MODEL COMPRISING A PROJECTILE BODY HAVING AN AXIS, AN EXTENSIBLE PROBE MOVEABLE FROM A RECESSED POSITION WITHIN SAID BODY TO AN EXTENDED POSITION, SAID PROBE BEING MOUNTED COAXIALLY WITHIN SAID PROJECTILE BODY AND SLIDEABLE THEREIN, GAS CHAMBER MEANS WITHIN SAID PROJECTILE BODY, A PORT IN SAID CHAMBER IN COMMUNICATION WITH THE REAR OF SAID PROJECTILE BODY WHEREBY PROJECTILE PROPELLING GASES MAY ENTER SAID CHAMBER UNDER PRESSURE, CHECK VALVE MEANS FOR LOCKING GASES UNDER PRESSURE WITHIN SAID CHAMBER, PISTON MEANS CONNECTED TO SAID PROBE, SAID PISTON MEANS BEING IN FLUID COMMUNICATION WITH SAID CHAMBER AND OPERATIVE TO DRIVE SAID PROBE TO THE EXTENDED POSITION WHEN THE PROPELLING GAS PRESSURE EXISTS IN SAID CHAMBER, AND MEANS FOR LOCKING SAID PROBE IN SAID EXTENDED POSITION.