Powerguns powerguns fire a burst of copper plasma at a significant fraction of the speed of light. Copper ions are held in alignment in thin plastic wafers which are fed throuthrough the weapon in a similar fashion to a conventional round. 

Power gun bolts are cyan streaks of almost blinding intensity. They vent their energy on the first thing they hit so their penetration is poor in forests and the like. 

Powerguns come in a number of calibres.  1cm pistols and submachine guns, 2cm shoulder weapons.  The 3cm tribarrels(basically 50 cals) and the 30cm main guns of tanks. The power to calibre ratio is logarithmic.