I found the Ueclid C-finder gun and I can't find the ARCH2 CHARGE ammo. I've checked in the game guide and have found nothing on it ,just the gun itself.

You need to complete Lucky Old Sun, and the laser recharges every 24 hours if I remember.

Complete lucky Old Sun and send the power to ARCHIMEDES II. Then the gun can fire once a day. It calls down thre beams of light that target the enemy and drop missiles on them. It's awesome.