[Panther Al]

As others said, loading the main gun on a M1 can be done really quickly- I could manage 3 seconds for the first 4 or 5 rounds before slowing - assuming the gunner was able acquire and fire that fast. On the move it was more like 5 seconds with the same comments as before, and this was the standard we trained to, not to mention the bragging rights of being the fastest - which I wasn't.

So. Let's say you haves loader and gunner with high enough initiative to get two actions.
Action phase 6: gunner fires and then loader begins loading.
Action phase 3: gunner aims and the loader finishes loading.

At least that's how I would do it: with the loader yielding first action in action phase 6 if the loader and gunner having initiative 6. If the loader has a 5, then even easier.