Well first of all an Enfield No5 "Jungle carbine" was never made in any other chambering than .303. If it is a genuine No5 Enfield then it's been converted and most likely to 7.62 Nato and not .308 Winchester. If it is a converted No4 or a No5 then you need to find a magazine which was originally intended for either the L39, L42,Enforcer, Envoy or a Parker-Hale T4. The genuine british Military magazines had a CR prefixed part number stamped on them. There was also another maker who's "Sterling" but their magazines were not of as good quality and often lead to feeding problems in my limited experience. Any conversion of a No4 or No5 Enfield to 7.62 Nato requires subtle machining modifications to the magazine well of the actions. This removes the feeding problems often found on conversions which have been done on the cheap.