to the mounting plate 32 have vertically oriented posts 34 mounted for axial sliding movement therethrough the posts are affixed at their lower end by means of a collar 35 to the housing 36 of the applicator gun 17 the posts are provided at their upper end with heads 37 adapted to bear against the pillow blocks and compression springs 38 surrounding the posts between the pillow blocks and the collars urge the vertical posts and the applicator guns thereon toward a lowered position as shown in fig3 the applicator guns 17 for supplying primer compound to the applicator tips 18 in a timed manner in predetermined amounts include an air cylinder 39 affixed to the rear of the housing 36 and a coupler member 40 affixed to the forward end thereof there is reciprocally mounted within the air cylinder a piston 41 carrying an o ring 42 in sliding sealing engagement with the interior walls of the cylinder an elongated needle 43 extends axially through the air cylinder piston and gun housing so as to be advanced and retracted with the piston an open ended adjusting sleeve 44 extends through the rear wall 45 of the air cylinder in threaded engagement therewith an adjusting knob 46 is provided on its end for rotating the sleeve 44 to axially advance or retract it through the wall 45 to selected linear positions the needle 43 extends.