HP PPSh 41 inner barrel

Hello gents, just thought i'd post up about the inner barrel on the HP PPSH. I purchased my PPSh from Airsoft world and on their spec it says that it has the inner barrel from a JG G36c (247 mm), I didn't check the length before ordering a new barrel (silly boy ). I luckily ordered a longer barrel (285 mm) as my plan was to make it as long as possible and cut the rest down.
Imagine my surprise when the new barrel arrived today and it was the same length as the original 285 mm.
I know partly my own fault but still it may stop some else making the same mistake.