Accession Number : ADP009075

Title :   A Consistent Method for Determining Gun-Tube Straightness on the M256 120mm Gun.

Corporate Author : ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD

Personal Author(s) : Wilkerson, Stephen

Report Date : SEP 1993

Pagination or Media Count : 13

Abstract : Currently, each 120mm gun-tube, as part of the manufacturing and inspection process, undergoes a series of measurements to determine whether the tube's centerline profile meets critical tolerances. The measuring a consists of a chain-driven plunger that is inserted down the gun-tube from the muzzle end toward the breech. At the same time, a laser device, which is positioned at the breech end of the gun-tube just in front of the forcing cone, transmits a laser signal to the plunger that records the location of the beams using a photo sensor. The true centerline is estimated as the straight line between the laser device and the plunger at the muzzle. Then as the plunger is inserted further down the gun-tube toward the laser, variations in the laser light are correlated with actual vertical and horizontal displacements to produce an estimate of the gun-tube's profile with regards to its true centerline. When a bullet is fired out of a gun-tube, the bullet is forced to follow the tube's profile. Due to the huge forces applied on the bullet by the propellant gases, considerable interaction between the bullet and gun-tube are possible during the interior ballistic cycle. These interactions manifest themselves in the form of out-of-plane vibration. (Out-of-plane refers to any direction other than the intended axial or down bore motion.) Shot to shot variations in those vibrations can lead to scatter and a loss of gun accuracy. Therefore, duplicating the current response of the system's dynamic behavior numerically requires an accurate representation of the gun-tube's centerline profile. This paper describes two methods for acquiring an acceptable gun-tube profile for use with numerical models of the M256 weapon system.

Descriptors :   *BORESIGHTING, *ALIGNMENT, *GUN BARRELS, *LASER APPLICATIONS, ACCURACY, BALLISTICS, BORES, DISPLACEMENT, DYNAMICS, ESTIMATES, INSPECTION, INTERACTIONS, INTERIOR BALLISTICS, LIGHT, MANUFACTURING, MEASUREMENT, MODELS, MOTION, PLUNGERS, PROFILES, REPRODUCTION(COPYING), RESPONSE, SIGNALS, SMALL ARMS AMMUNITION, TIME, TOLERANCE, VARIATIONS, VIBRATION, WEAPON SYSTEMS.

Subject Categories : Guns
      Ballistics

Distribution Statement : APPROVED FOR PUBLIC RELEASE