Looks like this mod is no longer being maintained, but in case anyone wants to run this mod with Pelagos, since one of its items has no magazine_size, need to change line 28 in prototypes/equipment.lua from
if magazine_item then
to
if magazine_item and magazine_item.magazine_size then
Thank you for help, there must be change in the game API, that I did not saw.
The magazine size was usually defined.
