Hi,
I was about to put some Thomastik-Infeld JS112 flatwounds on my 330, but not sure if it's a good idea. The strings are 12, 16, 20, 27, 37, and 50. I started to put the 50 on, and at first I wasn't sure if it would stay in the tailpiece because it's too thick, but then it seems it would. However, it doesn't really fit in the nut, sort of sits on top as opposed to completely in.

Plus, I'm not clear on if it's even a good idea at all to put this gauge on this guitar.

I got these because I read that this would be similar to what John Lennon used in the early days.

If I should not use these, can somebody recommend what flatwounds and what gauge? Would cheaper D'Addarios do the trick?

Thanks.

I use D'Addarios and they are fine. For your guitar, the 12s are too thick. They're made for a short-scale guitar like the 325. I use 10s on all my guitars, except on my 381 I use 11s for a nice fat Jazz sound.

If you change the string guage radically from the factory size, you will need to file the nut and saddle guide slots to fit properly. If you're going smaller, you'll need to purchase new ones.

I must disagree respectfully with magic fingers about a set of 12's. A set of 12's is not too thick. Yes, the nut slots and truss rods may need adjustment, and the saddles tweaked, especially the G string saddle to intonate a wound string instead of a plain string, but 12's are not out of the question.

Without going into all the math, a Rickenbacker 300-series neck is made to hold a 12-string set of 10's. By the time you get the tension of all twelve strings up to pitch, that is roughly the same tension as a set of 14's, if there is such a thing. So 12's will fit comfortably on a 330 neck with no stress, given proper adjustment. They may even sound better because the added tension over the bridge back to the tailpiece will help the guitar be more stable, and may actually improve sustain.

I do agree with magicfingers that a set of 11's is a good compromise set on a regular scale neck as they are not that different from a set of 10's, and will also help tone and sustain from the marginally increased tension. I prefer a wound G, so I use D'Addario XL115W: 11, 14, 21w, 28w, 38w, 49w.