How much damage would wooden bullets and rubber bullets cause?

Wooden bullets, probably not much. I’d have mocked the concept entirely, but apparently, wooden rounds used to be common for blanks, particularly as training rounds. Generally speaking, the powder detonation would reduce the bullet to sawdust when fired. Individually the fragments could be nasty, but not life threatening outside of a freak occurance.

There’s a persistent myth floating around that the Germans and Japanese issued them late in World War II. It holds that the rounds would splinter on impact and result in wooden shards that wouldn’t show up under x-ray. But, it’s the actual gunshot that shatters the bullet, which makes this whole myth a little suspect.

It looks like the Germans actually used them to launch rifle grenades, (a forerunner to modern under-barrel grenade launchers.) So they would have seen some use in the field. It also stands to reason most of the countries involved in World War II would have done the same.

Now, if you’re a soldier in the field, and your side is loosing, you’re ill equipped, running out of munitions, anything you can fire will look like a valid choice, eventually. So some people probably did get shot with these, but, I’m not finding any credible information that they’ll do anything.

If I was going out on a limb, I’d guess these could be lethal up to a few feet if you placed your shot correctly, but really these are blanks.

If you’re looking at a setting that actually requires wooden bullets (to deal with vampires, for instance), then you could make wooden bullets from a hardwood with a metal jacket to protect them from the worst of the powder charge, but I’ve got no idea how those would work in the real world.

Rubber bullets can kill. They’ve been kicking around at least since the mid-70s as a riot round. To their credit, they are less lethal than a gunshot, but they’re still pretty nasty. Rubber bullets are usually chambered for shotguns or riot guns (basically re-purposed grenade launchers), though there are a lot of different variants. This means you’re dealing with a very large, slow, projectile. And they still kill people.

If you really want to see what these will do you can just Google image search “rubber bullet injuries.” Just be ready for some really graphic content.

Rubber rounds for shotguns come as both slugs, and buckshot. The slugs are slightly more common, and alternately referred to as riot slugs.

Supposedly, rubber rounds exist for handguns. These are primer only cartridges (meaning no powder), and have muzzle velocities on par with airsoft. They’re intended for target shooting, though, I’ve never actually seen these personally, so I’m going by “things people wrote on the internet.” If the published muzzle velocities are trusted, these should be easily survivable.