How, when & why to lube your spring gun's piston seals
By B.B. Pelletier
You've asked about proper lubes for spring-piston guns, so I thought I'd offer some pointers.
Spring-gun piston seals are either leather or synthetic. It matters because there are different lubes for different materials. It isn't always easy to tell what's in your gun, so this may involve some research.
The gun's owner's manual is the best resource to consult about oiling, however most gun makers only recommend their own brand of oil and don't tell you what type oil is inside. So here are some tips for when you just don't know.
When in doubt, use silicone chamber oil
For most spring-gun seals, either leather or synthetic, silicone chamber oil is an ideal lubricant. It works best when used sparingly (one or two drops) in guns that have synthetic seals. RWS/Diana guns need one drop every 2,000 to 3,000 shots. Gamo airguns can tolerate a bit more - perhaps a drop every 1,000 shots or so. The models sold today don't really need that much. Other gun brands should get a drop every year or so.
Leather seals in spring guns need a lot more oil to stay flexible. RWS/Diana guns of the 1970s (models 25, 27, 35 and 45 rifles) as well as most other 1960s-vintage German and English spring guns can use 5-10 drops of silicone chamber oil every 500 shots or every six months.
Lower-powered guns with leather seals, such as the youth models made in the 1950s and '60s, can actually use regular petroleum oil. If you aren't sure of the gun's age or the piston-seal material, silicone chamber oil still works okay. Sparingly lube the synthetic seals of spring guns, but use a little more on spring-gun leather seals - and a little more often, too.
Use oil ONLY - and nothing else!
Do not use anything but oil in spring guns. Don't use moly, regardless of what you read. Moly that is suspended in solvents will diesel and may damage your gun!
Do NOT try to make spring guns diesel! Internal combustion fuels - diesel, kerosene and similar ones - will explode in a spring gun, causing SERIOUS HARM to the shooter! Even petroleum oil can diesel in a powerful gun! If it explodes, it can cause gun damage and possibly injure the shooter and those standing nearby.
Some target spring guns, such as the FWB model 300 rifle and model 65 pistol, have seals that self-lubricate and do not require any additional attention. Just shoot and enjoy.
Old gun won't spit out a pellet? Rejuvenate it with oil!
When a gun with leather seals won't shoot a pellet out the muzzle, put 10 drops of silicone oil down the muzzle and stand the gun with its muzzle pointed up for two hours. The oil runs down the barrel, through the air transfer port and into the compression chamber, where it soaks into the leather seal. Usually, this rejuvenates the gun.
If your gun is spitting any sort of material into the barrel, STOP SHOOTING IMMEDIATELY! That material is the piston seal breaking up and being expelled through the transfer port. Repair it before shooting the gun again.