p226/9 in 40 shoot 9mm?

[MT2008]

What GM said. You would need an entirely new top end.

If you want a 226 at all, just buy a 9mm - specifically, one of the older German-made guns. Don't buy one in .40 or .357; the 226's magazine capacity in those calibers is identical to that of the 229, so you might as well just get a 229. And unlike the 226, the 229 was designed from the ground-up for those cartridges.