G36 hop for xm8

[krap101]

I'm eventually going to try to make all my xm8 internals metal, so starting with the hopup. If i get a g36 hopup, will it make it compatible with g36c mags without modification? From the pictures online the feed from this one compared to the present hop up looks totally different http://store.matrixbb.com/servlet/-s...l-Hopup/Detail

and essentially all g36 mags are the same, like g36c and g36k and stuff

also how long are xm8 inner barrels? i've been reading that its slightly longer than the g36 so i should go with an m16 barrel?