I hate to seem like a complete idiot, but it looks like I am going to have to stick my neck out and ask. Is it really worth all the trouble to go with the 40mm, or just stick with a 37 and reload your own shells if you aren't looking to to find HE or incindiary?
I have even seen "bird bombs" at the gun shows for the 37 mm that would lob around 50 yards, then boom!!!!! Ddesigned to scare birds off of your property. I would guess in this instance the definition of birds is fairly loose.