Abstract: An assembly for effecting a variable volume chamber for use in a cannon having a breech assembly operably coupled to a chamber, and includes the chamber having a certain size being partially defined by a constant diameter for a known depth dimension and having a known volume and a breech plug assembly disposable in the chamber to a selectively variable depth, the depth being less than the known depth of the chamber such that the plug fills a first selectively variable portion of the known volume of the chamber, thereby leaving a second variable portion of the known volume of the chamber free and defining a chamber variable volume. A Cannon including the variable volume chamber and a method of effecting a variable volume chamber are further included.

Abstract: An assembly for effecting a variable volume chamber for use in a cannon having a breech assembly operably coupled to a chamber, and includes the chamber having a certain size being partially defined by a constant diameter for a known depth dimension and having a known volume and a breech plug assembly disposable in the chamber to a selectively variable depth, the depth being less than the known depth of the chamber such that the plug fills a first selectively variable portion of the known volume of the chamber, thereby leaving a second variable portion of the known volume of the chamber free and defining a chamber variable volume. A Cannon including the variable volume chamber and a method of effecting a variable volume chamber are further included.

Abstract: A battery impedance measurement apparatus for battery powered implantable medical apparatus in which current source means and reference impedance means are selectively connected across the battery after it has been isolated from the medical apparatus, and the resulting currents of interest are digitized to provide a factor directly related to the value of the internal impedance of the battery. The digitized value may be telemetered out of the implanted medical apparatus to enable critical decisions to be made based on the remaining life of the implanted battery. The same measurement apparatus can be used to form an accurate end-of-life signal.