I carried the exact SIG P320 equipped with a red dot and night light in a polymer holster for the past 7 years. It shot well, and I never had an accidental discharge. Needless to say recently they were all traded for Glocks.
I am seeing more gun ranges post rules online and at the range prohibiting the P320 from being brought onto their property. Banned. No sale, trade, carry, shooting, or repair work on the P320 is allowed.