Q: I want to put heavier-gauge strings on my electric. It shipped with .009s, but I want to go at least to .013s. Is that possible?
A: Back before the dawn of the light-gauge or “Super Slinky” strings, all electrics built in the 1950s and ’60s came standard with what we’d consider fairly heavy-gauge strings, which included a wound G string. Going up from .009s to .013s will probably be okay on most solidbody guitars, but keep in mind that most hollowbodies are set up for what the manufacturer feels is the best set of strings (usually .010s or .011s). Strings put an enormous amount of pressure on a guitar’s body and neck and heavy-gauge strings mean even more pressure, and this is what you’d be most concerned with when putting a set on a hollowbody guitar like a Gretsch 6120. That being the case, we’d suggest contacting the manufacturer about warranty issues before making the change, even on solidbodies.
At the very least, you’ll need a pro setup after restringing with heavier gauges to keep the intonation accurate when playing up the neck. You might also need the nut to be modified to accommodate larger strings. Finally, the truss rod may require a tweak to keep the neck straight.
The best course of action is always to consult a qualified guitar tech when making changes that are “out-of-spec” from the way the guitar shipped from the factory.