All our small arms including GPMG are looked after by the Gunner's party (Warfare Specialists). There is one armourer onboard, who is a CPO/PO ET (WE). He will attempt to rectify any defects with small arms but day to day maintenace and cleaning of small arms remain with the users(Gunners)
If ordinance is your bag as a WE you will assist the CPO/PO (WE) in looking after miniguns, 20mm/30mm cannon, 4.5 inch gun (obviously dependant on what ship you're on).
But weapon engineering encompasses a whole raft of systems.
External Communications (including Satellite Comms)
Internal Communications (onboard phones and telephone exchange)
Electronic Warfare sensors and Decoys
Computer assisted Command systems
Gyros and navigational aids
As an ET (WE) you will get time to work on all these systems in your first sea job, but on promotion to leading hand and onwards you will specialise in one area of the above.
Myself as a WE i look after my ship's surveillance radars and subsequent seawolf system.