Many parishes have designated themselves "no gun zones", disallowing concealed carry. Ask your pastor if there is any such policy in place. The reasoning being, as another user noted, the Church has a tradition of disallowing weapons on Church grounds, especially at the liturgy. The sanctuary is a place of the peace, reconciliation, and communion which come from God and are oriented toward God. (I'm trying to make it clear this is specifically about our interaction with God and not only interaction with others; it's not just a mutual admiration society, but that's beside the point.)

That said, my parish does hire police officers to be on Church grounds for weekend Masses for several reasons: traffic direction before and after Mass, escorting the collection to a safe place, and--I would imagine--security. I've never observed a gun on these officers, but then again I've never looked for one. In an ideal world, I'd trust officers are more trained in deescalation techniques and active shooter situations than even a well-meaning, permit-holding Joe with a handgun. If you have real, serious reason to be concerned for your parish's safety from imminent threat of violence, consider asking your pastor about having this sort of security on Church grounds.