Mine is a 1969 D-18 Martin. I've been using medium guage (i.e., "13s") phosphor bronze happily enough for years. The Martin SPs are phosphor bronze, and are one of the brands I'll generally buy.

I don't change strings very often. Like a few others among you, I don't particularly like the extra-"bright" soung of brand new strings, and prefer the sound after they've been played for a least a week or so. Of course, at some point, the sound gets dull enough to require replacement; I usually wait well past the optimum time to change.

(Years ago, when I played very long hours on the street, whaling away as hard as possible, I'd break a string or two and buy a new set before too much wear set in. But now, playing a bit more quietly and not so constantly, my strings last long enough to become dull-sounding before they actually break.)

Last time I bought strings, I decided to try elixers (not Elixer brand, but a less-expensive competitor) on the theory that they'd hold their tone longer. Seemed to be a good idea for someone who postpones restringing as long as possible.

Bad idea. For some reason, this type of string produced fret buzz, notably on the B string. I got new frets and a neck reset a couple of years ago, and enjoy lower action than ever before. I have no problem with my customary medium-guage strings, but when the luthier gave me my guitar back strung with light-guage 12s, I experienced a bit of buzz after playing for a while and beginning to strum with abandon. Switching back to mediums solved the problem completely.

But these medium-guage elixers caused a much greater problem than the non-elixer lights. One string in particular, the B, buzzed consistently, even when played pretty softly. I had to replace the B string with its predecessor, the Martin SP string I had just taken off the guitar. Problem solved. I expected a noticable difference between the one old string and the other 5 newer elixer types, but it doesn't seem to be an issue.

Next set, of course, I'll be going back to my old standby phosphor bronze mediuims.

I might try those brass bridge pins. My set of black plastic pins is pretty chewed up (inside the bridge, where you can't see the damage) but perfectly functional; however, for a mere $14, I can afford to splurge on this next experiment.