yeah, you should be good with the practice balls. you may need to use some wadding or sabot to seal it in

interesting choice of round....potential knuckle ball or, depending on your choice and precision of your sabot, could end up as a giant bb with weird to no hop up

should be fine if the round has enough weight.

cannon balls don't need hopup to travel far and straight




edit:

btw, a good round to shoot are bean bags. well, I never tried a bean bag but I did launch one of my nieces bean bag toys and it went pretty straight. lol

The practice balls are slightly larger than 40mm in diameter. There is actually a video of a guy on youtube using the same shell firing one of the light weight balls and goes pretty good :D

you know that a 40mm launcher isn't 40mm right? :p

Whatever they size I already know they fit, snugly :p

But that being said an M203's bore diameter is supposed to be 40mm according to the US Army. :D

but being able to fit real 40's in a toy launcher is a big no no.

but to confirm it, a friend had a LEO try putting his 40mm round in the CAW revolver. didn't fit.

Well this IS airsoft and not the real thing :D

Last thing you'd want is someone throwing a real 40 mike mike into an airsoft launcher to see what would happen :p

ya...our stuff is around the 37mm-ish mark

None of the sizing maters anyways :p

But I was just over at a friend's and his Madbull launcher measures 41mm in Diameter with the calipers. Guess I'll check the king arms when it arrives on thursday