Speer makes empty shot capsules for reloading in both calibers.
You can see one main difference in the shotshells; their relative size.

I have loaded them with shot as small as #10 shot and as big as #8 shot. Smaller has a denser pattern, while bigger hits harder.

Speer recommends 5.5 grains of Unique in the .38 Special for 1128 fps. They recommend 7.5 grains of Unique in the .44 Magnum for 1254 fps.

My experience is that they both work well for snakes, but the .44 has a much better shot pattern.

To load the shells, I take the empty capsules and place the shot in the capsule.

.... then seal it with the plastic plug.

Keep at it until you have enough to reload a batch.

You resize and reprime the empty brass as normal, charge it with powder, and place the shotshell in the case.

It is seated on the powder and crimped tightly.

You're ready to go.

Notice how deeply they fit into the case.