Maybe you could make them more customizable with “Modifications”

Exe 1: You Could have different types of bullets with different effects?

Iron Nuggets ( lets use this as a “base” bullet for this example):
Damage: Normal
Armor piercing: normal
Player injury(just a stuttering slowness effect, as if you were wounded): Normal

Gold Nuggets:
Damage: Below Average
Armor piercing: Below Average
Player Injury: Above Average (malleable, equivalent of rubber bullets, nonlethal, but good to incapacitate)

Diamond:
Damage: Below Average (Imagine stuffing a diamond in a gun, it would be a crude bullet)
Armor Piercing: High ( it would be hard and armor pierce-y I guess, only exe)
Player Injury: Below Average

Charcoal:
Damage: very low
Armor piercing: very low
Player inury: High (As if you were shot with a hot coal)

Exe 2: More Customizable guns/ Gun forging

Er… maybe you could shift+rightclick on an anvil with your gun and get a gui with these mods:
Barrel Length:
Short: Less accuracy, quicker load time
average: ok accuracy, regular load time
long: great accuracy, LONG load time

Body Material:
Wood: Light, increased movement speed while aiming (needs to be repaired often)
Iron: Average, regular movement speed while aiming ( doesn’t need to be repaired often)
etc…

And you would have to repair them as well.
PS: it would cost resources to modify, like, y’now, wood and iron