Contact your issuing agency.
This issue has been brought up and each issuing agency handles it different.
Some will not allow you to carry the handgun in another caliber.
Some will list the handgun with the additional caliber.
You need to contact your issuing agency prior to carrying it in the other caliber.
"If someone has a gun and is trying to kill you, it would be reasonable to shoot back with your own gun.” - Dalai Lama (Seattle Times, 05-15-2001).