The objective of this demonstration was to eliminate the environmental and health hazards posed by the current M1 propellant and the lead foil in the 105mm M67 propelling charge. The benefits of this effort are elimination of lead from the production process and elimination of ground and air contamination due to demilitarization processes. The M67 is a seven increment bag charge system used in the family of 105mm artillery cartridges. The charge uses M1 propellant, a single-based propellant that has two different grain geometries; a single perforated (SP) grain, used in zones 1 and 2, and a multi-perforated (MP) grain, used in zones 3 through 7. Lead is currently present in the form of a foil lining inside the zone 5 cloth increment bag. The lead is used as a de-coppering agent to “clean” the gun barrel of copper residue from the copper projectile rotating band. In addition to lead in the M67, M1 propellant contains other environmentally harmful chemicals – dinitrotoluene (DNT), dibutylpthalate (DBP), and diphenylamine (DPA). The objective of this effort was to replace M1 propellant with M64 propellant to provide environmental benefits on three fronts: elimination of direct Soldier contact with lead, elimination of lead, DBP, DNT, and DPA from production and manufacturing processes, and elimination of ground and air contamination due to demilitarization processes. ESTCP provided funding to manufacture two lots of propellant, perform the full suite of testing necessary for the qualification, and leverage funding from program manager combat ammunition systems allowed the low rate initial production (LRIP) of 5,000 lead free M67’s.
The formulation of PAP7993 propellant was developed at Picatinny Arsenal and is currently fielded in the 155mm Modular Artillery Charge System (MACS) M231 propelling charge. With minor dimensional modifications to PAP7993, M64 propellant is a viable, low risk candidate to be inserted as a drop-in replacement to M1 propellant in the M67 propelling charge. As with M1, M64 is also a single based propellant, with two different grain geometries. M64 contains a non-toxic de-coppering agent in place of lead and is formulated with stabilizer and plasticizer constituents that reduce harmful environmental impact. With M64, the M67 propelling charge achieves the same ballistic results without altering the propelling charge bag design. M64 will be a drop-in replacement for M1 propellant in the M67 Technical Data Package (TDP), and be a transparent change to the end user with no significant impact on logistics and operations.
The qualification of M64 was broken down into two phases; a confirmatory phase, and a reproducibility phase. The first phase consisted of producing a confirmatory production lot of M64 to conduct laboratory and initial ballistic testing. The second phase consisted of manufacturing a second “reproducibility” lot of M64 and a final rigorous ballistic test – the 105mm firing table ballistic (Ftab) match test. The Ftab test is well known to be the definitive test for new propellant as it compares performance parameters such as muzzle velocity, range, and extreme temperature performance. The results of all tests were highly successful. M64 propellant matched the ballistic performance of M1 and, in some cases, M64 exceeded the performance of M1. The qualification process for M64 is complete and with this ESTCP demonstration the propellant is fully qualified and was added to the 105mm M1 High Explosive technical data package (TDP) in 2019.
M64 was shown to be a drop in replacement for M1 propellant and meets or exceeds all performance parameters. There are no expected issues with transitioning this technology. The propellant manufacturer, Radford AAP, has been producing a variation of this propellant for over 12 years for the 155mm M231 charges. Radford has demonstrated that they have the knowledge and capability to produce this propellant. Radford currently produces over 500,000 pounds of PAP7993 a year for the MACS program and has the capacity to make more. Scaling up the M64 for 105mm use fits into their capacity. The operations of the Warfighter in handling the ammunition will remain the same and there are no logistical or fire control impacts. By March 2020 lead will no longer be used in the production of the M67 propelling charge. This project will reduce lead used in Army operations by over a half ton per year and eliminate over 250,000 pounds of known environmental contaminants per year.