A contact tip for a welding gun having a central passage for a welding wire moving in a given direction toward a workpiece and receiving a welding signal by contact of the wire with the tip. The passage has an innermost end, an outermost exit end and a length of at least 1.5 inches and an opening in the contact tip intersects the passage so a pressure block slidably mounted in the opening is biased toward the wire by a spring around the contact tip urging the block against the wire. This tip is dimensioned and constructed to perform pulse welding by a relatively ductile aluminum wire.