No they are different in their range . 40mm from a Mk-19 is high velocity and from the M79, M148and M203 it is low velocity. Not interchangeable at all.......
As well the point and area targets are different . Consider the point and area targets of the old M60 GPMG. They are almost identical to the Mk-19’s ammo. 1100 meter point....:o)
Mk-19 has it’s place and is a sweet accessory to the M134D or DT versions and Ma Deuce !
Greatest tools every made for a gun truck !
In your EOD life, did you ever come across that Russian caliber naming quirk, ie, not naming different ammo types the same millimeter number? I read in a book by a Russian that they could not believe in the USA we had 81mm this and 81mm that. They thought this was stupid, and was bound to lead to battlefield errors, due to bad radio transmission or whatever. Instead of desperately needed mortar rounds, you would wind up with a delivery of recoilless rifle ammo, for example. So this Russky said all Russian ammo, bombs etc were given different mm numbers, even if their calibers were identical. Did you ever hear this?