Thread: HXP 303 ammo corrosive? found rust in my barrel

Been a while since I used my enfield, but put about 20 rounds of Greek HXP through it.
Noticed rust in the barrel after pulling it out today.
Is this just from moisture or from the ammo? I was pretty sure this stuff is supposed to be non corrosive.
It appears it might just be at the last 50mm of the barrel from what I can see.
I put a cleaning patch through after shooting, with a light oil, but that's about it.