The information on the S&W website does not explain whether there are any internal safety mechanisms for this gun without the thumb safety. It also does not have a lock or magazine safety. Is this similar to a Glock that has three built in safety mechanisms?

I have a mp 9c with no thumb safety. It will fire with out a mag. As far as I can tell the two stage trigger is all the safety that is built into the gun.

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Wrong, All M&Ps have a trigger safety and the striker block safety some of them could have or not a mag drop safety and some of them have the thumb safety added.

The guns are safe. The only way a loaded gun will discharge is if the trigger is pulled.

When my agency was T&E ing the M&P system 7 years ago, we removed the firing pin safety from one gun to test the trigger safety. Loaded with a pried casing, that gun was submitted to some abuse to simulate being dropped from every imaginable situation. The trigger safety alone was enough.

Please remember this was done only to test the trigger safety. After this portion of the testing was complete, the firing pin safety was re-installed. I would never recommend deactivating any of the safety features.