All 416 will have "problems" with front ends, since it's not designed the same as a standard M4.
If you want to swap the front end, why choose an HK416? They are (in airsoft) pretty much the same as an M4, except their front end and upper receiver are higher and has a continuous rail.
Internal parts are the usual V2 parts.
@Moretoasties: The bolt wasn't stuck open. It has a bolt lock feature. Just pull then release the bolt handle, it will close. Or, push on the handle and it will close too.
Last edited by Conker; November 30th, 2009 at 18:40..