well in terms of metal bodies id still go with VFC or King Arms externally, G&P is great as well, but for a cheap economical good grade metal body i would go King Arms
im a KA fanboy!!!
VFC HK416 Custom
Custom Bowie Tactical x SAI Glock 17 (TM Base),
Custom SAI BLU Glock Build (Timberwolf Base)
Custom Zev Noveske Shooting Team Glock 34
Custom Zev Dragonfly G17 (Project) (In progress)