Does EMG x Retro Arms CZ Billet CNC 8mm Ver.2 Gearbox Shell fit umarex/vfc hk416a5 avalon v2? If not, whats the better option for 450 fps DMR build?

I want to build an dmr from my umarex hk 416a5 and im kinda lost its the first time making a build, ideas will be preaty much acepted.

Thanks in advance .