Springers are amazing fun when you're just out to have good, cheap fun and not worried about having too much realism.
Just put a thin layer of silicone oil all over the insides... Anything that movies. It's a good standard to go by.
RS Type 56-1 & RS Type 97B & KWA M11A1 w/steel kit
KJ M1911A1 & KSC G19 + AI Grenade