"Oh boy, this room gives me the creeps, we better prepare ourselves before going in to fight whatever gatekeeper is there. Except for me, of course. I'm gonna use the same weapon and no extra armor, even though I don't think I can fight whatever is in there. Jeepers, look at that huge thing, our party's best magic attacks barely did anything. Should I change into my super ultra deluxe OP armor and maybe one of my many high powered futuristic weapons or rocket launchers? Golly no! I'm gonna keep using this dinky battle rifle that is proven not to do much against this terrifying enemy. Mercy me, why isn't this working as well as I'd hoped?"
There's a line between conserving CP and being suicidal. MC is clearly sick of life. Also, does he need to repurchase every weapon he takes out after putting it back into the system? I thought the point was that he was an experienced player with a shitload of weapons and armors. Does he really not have any sort of stockpile of ammunition? I kinda feel like we'd know better if the MC is super retarded or only regular level retarded if we knew how much CP ammunition actually costs.