What kind of medieval armour and weapons can you make using today's sciences?

[Aedilred]

Canister OTOH is fantastic. It had half again the range of a musket and fired much bigger rounds then grape, it helped end linear tactics because standing and exchanging fire with cannister rounds was suicide. That is why Napoleanic tactics had so many bayonet charges. Even if the 3 inch balls didn't kill it I'm willing to bet they shatter the dragon's wings and it falls from the sky.

Then rifles became popular and had more range and canister disappeared again. A sad day for cannon kind.

Ah yes, canister is great stuff (if you're trying to kill people). But true canister is pretty decidedly modern (as opposed to medieval). That said, the principle isn't that complicated and doesn't require electronics or special chemical compounds to create, so depending on how we interpret what we're permitted by the OP, I guess we probably do have it available.