The GK1 fires pellets and slugs from the magazine at high velocity. It does so with a fair amount of force. This creates lead dust that, in extreme cases, can get into just about everything.
In that case, a good cleaning is definitely a must!
Here’s a photo of what the inside might look like. So, grab some cotton swabs and brake cleaner or rubbing alcohol.
After that, you might notice a drop of oil or a smear of grease here and there. You can prevent this buildup by not setting the power setting too high and by cleaning off any visible residue promptly.
Of course, it’s still a semi-auto air pistol that’s just begging to be used a lot :-)