The MG131 wasn't a particularly fast firing gun. The 88mm shell fired by the Tiger tank was electrically primed. The 88mm shell fired by the FLAK gun wasn't.
Other examples exist.
However, we are getting a bit afield as caseless rounds, firing conventional bullets are not the 100# non-metallic round the OP is asking about.
As previously mentioned, what does one use for a bullet that isn't metallic, but can come at least somewhat close to metallic bullet performance?? And, at what range?
The most useful material that I can think of right now that isn't metallic would be stone. the first cannons shot stone balls. But for small arms, possibly useful but no where near the utility of lead, copper, or steel.
Solid stone (in a sabot) would survive firing, but won't perform like metal when it impacts. Likely shattering on anything hard, and certainly not up to expanding while staying together. Perhaps stone powder in a polymer matrix?? Anything else out there that approaches the density and malleability of metal for bullets??
Wood could work, but again only at very close range, and to stop the vampires, you have to hit them in the heart...
High density plastic could work, but again, despite uber high velocity possible, the very light projectile sheds it very, very rapidly. NO military, police, or even sporting interest in bullets that have a lethal range of only a double handful of feet, let along yards.
There is, however, a tactical niche I can see them fitting in. Self defense. Inside the house/very short range / belly to belly distance. This might even be a "better mousetrap" in certain situations. Barrier penetration would be about zilch, so all that worrying about shooting through walls and hitting others is very low. Penetration of unarmored human? Some testing needs to be done. Perhaps one might find something that reliably goes half way through (reaches vital organs) but does not normally exit??
Big plus if you can make it to work in existing guns, too. No idea if a plastic bullet (even at 2-3000fps from a pistol) would have the recoil impulse needed to operate the standard tilt barrel recoil operated design. Again, testing is needed.
Caseless ammo, using "regular" bullets has been tried, and has had limited success but not enough, so far for serious military consideration.
The basic problems are
forming the powder into a solid that will survive the rigors of handling, shipment, and the feeding cycle of the gun, AND ignite reliably, AND burn cleanly enough that residue doesn't build up in the chamber preventing chambering further rounds.
The biggest stumbling block not mentioned is HEAT. Extracting and ejecting the brass (or steel
) case removes a lot of heat from the chamber. Also the heat resistance of the case though slight, does delay cook off of chambered rounds a bit. This is another side of the coin with caseless ammo, and modern combat firepower requirements.
And, bear in mind, that any firearm design for caseless rounds still needs some kind of system for extracting an unfired round from the chamber, and ejecting it from the gun, so the gun can be unloaded. AND something better (if possible) than a rod down the barrel for clearing stoppages, which ARE going to happen.
Lots of things to consider, and to date, we haven't come up with anything that can do all of what we want done, better, or even as well as the brass cartridge case we currently use.
