I've posted here before about getting an M203, and now I think I'm ready to do it. I intend to get an LMT or Colt receiver and a DSA or LMT barrel. I am posting about ammo and reloading info. I have seen references to grog's reloading data. I am primarily interested in reloading chalk which I've found some data on, but would also be interested in reloading buck shot, and if possible, bird shot. I am not interested in explosive or incindiary ammo. I signed up on the grog forum but have yet to be approved for membership. I'm looking to order the receiver in a week. For my purposes, is buying the reloading data worth it? I kind of want to understand what loads are in the data before I buy the data or a launcher.

For what you're specifically interested in, no, you don't need the reloading data at all. I'd still buy it, it's $75 and really does open up the options - including non-explosive, of course.

You'll do well to buy a Cannon round from http://reloadableshells.com/ for big payload (55 #4 buck pellets, as an example), but honestly it sounds like you'd be quite happy assembling chalk rounds and using a 12ga to 40mm adapter... perhaps the 4x410 to 40mm, as well, which is honestly a lot of fun but takes longer to reload than just slipping an empty hull out of a single-shot adapter.

I picked up my beloved LMT 9” 40MM which is rail mounted under my M16. I have always been crazy about a secondary barrel and the look is just plain sexy. I ONLY shoot the beehive round out of mine so can only tell you about that but man, it is good to go and .22 rounds and primers are cheap and plentiful. Plus if da bad guys or zombies come, the beehive will be more than sufficient to punch their ticket for that dirt nap versus shooting chalk at the enemy. Practicality is key unless you just like playing with chalk....just sayin

I didn't buy it to be practical.

I did order the data. I haven't received it yet.