Okay then how would he do anything to any of the super armor characters like cybertronians, who have regular bullets bounce off of them? And have gigantic high-powered weaponry that would reduce many a character to cinders as long as they're moderately close to the impact site without even needing a direct hit? But, okay, fine, if you're shutting down that particular ability that's more or less the entirety of what Cliff can actually do, unlike everyone else who gets a myriad of powers both magical and physical, I've got two solutions in mind.

One, I reduce the actual piercing power so it's more like just a decent impact that works against the other amazingly powerful characters because Hol can hit them a whole lot with some good accuracy and the more bullets he has out the harder it is to fine-tune them. For a less The Emperor style thing, I can use multiple shot types instead. One per each cylinder, for a total of 5. I retain the infinite ammo and lack of reload for all shots, then they have different properties. Something like

[list]
[*] [b]Cylinder 1:[/b] Regular bullets of some undetermined caliber. Negligible recoil, excellent firing speed, used for spray and pray.
[*] [b]Cylinder 2:[/b] Spreadshot, fires a cone of buckshot like effect, smaller effective range and some recoil but easily able to catch multiple enemies and packs a lot of force.
[*] [b]Cylinder 3:[/b] Armor piercing shot, emphasis on armor penetration at the cost of internal damage and firing rate
[*] [b]Cylinder 4:[/b] Trick shot, able to curve around obstacles, precisely ricochet off surfaces and the like, but needs concentration in order to work just right.
[*] [b]Cylinder 5:[/b] Explosive shot, can only have one of these active at a time, can be detonated on impact or at will for traps, more widespread damage but dangerous to the user if in close proximity.
[/list]

I just have to express how unfair I think this decision is considering Superman up there has been approved because there happens to be magic, even though he could still fly at threats at absurd speeds and paste them or otherwise avoid damage, and the number of characters who have firepower equal or greater than my guy at their beck and call and also have any number of extra abilities both offensive and defensive to back them up and let them engage in other kinds of combat or survive well beyond Hol's abilities.