Abstract: Apparatus and method of improving the performance of a pump for pumping fireproofing material and the like viscous materials is disclosed wherein the pump is the type which includes a compression chamber (44) having an inlet (48) and an outlet (50). A piston cylinder (19) is disposed in fluid communication with the compression chamber and, a piston assembly (A, D, G) is carried in the piston cylinder driven in reciprocating suction and compression strokes. The piston assembly includes an extended piston (B,E) carried on a push rod (18) having a piston face (42, 61) terminating adjacent an inlet ball limit pin (52), having a reduced pin length of 5/16 inch, at the end of the compression stroke.