One more photo from my personal stash. I learned yesterday that the term "Sabot" for a piece of metal that seals a shell in a barrel and then flies off when it is fired dated back to before the Civil War. Those re-creators we saw yesterday had Sabot Shells on display that worked with 1860-era rifled guns.We used time fuses on our projectiles that did the same. The FDC (Fire Direction Center) would calculate the distance and time needed for an airburst and we would set that on our fuses. For our smaller howitzers we had what was called a beehive round which was similar to the coffee sized canister you referenced and was used just like a big shotgun when shot. Used for enemies that got to close for the normal rounds used by artillery.
It reminded me of this photo my buddy Andrew, a news photographer traveling with me, took in early March 2003 in Kuwait as M1A2 tank gunners live fired to zero in their main weapons before rolling into Iraq. Look a couple yard in front of the barrel and you'll see a Sabot Round breaking apart as the projectile goes forward.