20/22 gauge wire OK for 40 watt bulb?

[DIYMark]

I have an existing switched outdoor light that I want to add an unswitched feed to. The idea is to have the unswitched feed controlled by a motion detector. The problem is the outdoor light has a small decorative tube that the wires feed through to the j-box. So I can only get small wires through it. I did some quick calculations (check me here) and since I want to use a 40 watt or less bulb it should only draw .3 amps max. So it would seem that I could use some 20/22 gauge wire (300v rating) for the task. The distance from the planned socket and j-box is about 12 inches. Is this a reasonable assumption? If the worry is that someone later could install a larger watt bulb...hence the code to use 14AWG I could put in one of those decora bulbs (small socket base). I've never seen more than 40 watt bulb available for those. Any feedback is most appreciated.
DIYMark

[imported_joed]

You can't use anything smaller than #14 on a 15 amp circuit. Can't you connect to the existing wires coming out of the lamp? Your connecton must be made in aproved boxes as well.