I've already posted pic of my HK51 earlier in 2005, but now it's a bit more upgraded.
Externals: TM MC51, TM optics claw mount, Arsenal 3-9x40 scope, 25mm scope rings, custom silencer (hexkey mount), CA G3/SG-1 stock, Guarder reinforced steel pins
Internals: Systema 6.04 barrel 470mm, Sanyo 12V 1300 mA*h battery (large type), Guarder steel gears (original type), custom metal bushings, TM Type-0 cylinder, Systema silent-head set, Systema spring guide with bearing, Systema M*** (too high for this forum ;-)) spring