Yes, they can - you can use a tiny (map_loop.script) to share current-ammo between different weapons.
eg- this shares ammo between "weapon 3" and "weapon 5" in my game:
player check heldweapon global.heldweapon
if $global.heldweapon == 3 {
player check ammo 3 global.weapon3ammo
take ammo 5
give ammo 5 $global.weapon3ammo
}
if $global.heldweapon == 5 {
player check ammo 5 global.weapon5ammo
take ammo 3
give ammo 3 $global.weapon5ammo
}
Here's a video of it in action...the "gun" and the "zoomed-gun" are actually 2 different weapons sharing the same ammo
https://dai.ly/k3DKagrsOzAFqIH4USy