Ian, I was fan of apx100. Used a lot of it in 94 to 98. It was notorious in the market for being the iso 100 film with he biggest grain. As a matter of fact, it was never even marketed as a fine grain film while tmax' motto was "fine grain".
No, it wasn't. Popular Photography did a comparison of 100 speed films and it won overall, and none were particularly large grained.
I still have some frozen, unopened boxes of 4x5. Great stuff.