Looking for guidance in Riverside.

[five.five-six]

Am I allowed to change the barrel on my .40 guns and carry .357 sig?

[EsotericEpsilon]

For CCW, if it was originally DROSed in .40 then it must stay in .40
If you want to switch caliber, you have to update DROS (pawn-return), then update your CCW if you already have it. I've had to do the same when switching from 9 to 357sig. I'm not sure if you'd have to requal when updating. I did mine before I qualified with my firearms and had no problems.