Anyone specifically have problems with the .118 gauge Circle K?
 

I have a four string (B Standard) and a five string (A standard) and I use Circle K Strings on both. On my four string, the .118 is the low B, and the low D on my five string. On both strings I've noticed a sort of airy buzzing sound when slapping striking them agressively, but on this gauge and brand specifically (not any other string). Has anyone had any problems with this, or could enlighten me as to what could be the problem?

I noticed something alike with GHS strings. I think, but am not sure, it's caused by slightly loose windings.

Have you tried a heavier gauge? That's pretty darn light for a B or D, and CK's are already pretty floppy. I think what you're hearing is just the string not having enough tension and is buzzing your fretboard.

I have tried heavier gauges, and it's definitely not buzzing against the fretboard.

Now that I check my basses, I notice that the 4 string's B peg barely even has a full winding, and the 5 string's has about one and a quarter. This could very well be the problem.

It might be an unlucky combination of core and thread wrap sizes used to achieve that particular diameter.

It is too bad their sized jump to either a .112 or a .124 because that makes comparison a little more invasive to your setup.

Maybe try somebody else's .120, in either steel or nickel, on a whim. It would not be the first time someone has used a different formula for their lowest string.

Yeah maybe push down on the string behind the nut and give it plenty of pressure and see if the buzz goes away.