Lubrication
Any type of high-quality, medium-weight lubricant (oil) specifically
designed for use on firearms such as Break-Free (C.L.P.) Ballistol, or
Militec will work well on the HK USC carbine. DO NOT use
lubricants/cleaners that boast of their ability to penetrate metal (i.e.
WD-40, Tri-Flow, etc.) as these substances may deaden primers.
Where and how much?
No Lube – (surface is dry and not slippery to the touch)
Sling material
Plastic components
Light Lube – (finger run across surface yields little or no lube)
Bore and chamber
All metal parts (except sound suppressor)
Muzzle
Magazine spring
Axles of all operating controls (cocking lever, bolt
catch, safety/selector lever, magazine catch, etc.)
Rear sight assembly
All metal accessories
Medium Lube – (finger run across surface yields some lube but lube
does not run down surface when held in a vertical position)
Bolt group with recoil spring and guide rod
Heavy Lube – (Lube runs down surface when held in a vertical
position) No heavy lube is required on the HK USC!
Reapply lubrication to the bolt of the USC periodically during firing as
it burns off from the heat.
Apply lubricant using a shaving brush, swabs, patches, or rag. A spray
bottle also works well using compressed air to circulate the lubricant
into all parts and to remove the excess.