I just had a Leupold DeltaPoint Pro mounted on a M&P9 Pro CORE. The iron sights do not co-witness as the DP Pro sits too high. I used the Leupold mounting plate adaptor for the CORE. Just a FYI ...

Got me wondering, what red dots do co-witness? Interested in hearing other folks experience.

The Vortex Viper co-witnesses perfectly on the M&P Core, I mounted mine two weeks ago. It co-witnesses so much the sights obstruct the field of view a bit and I am considering removing the iron sights. I'm really liking the Viper though.
SB

The Trijicon RMR will cowittness as well.

I have used an M&P 9L Pro CORE 5" 9mm (m1.0 with full Apex cures) and a Venom sight. Works very well.

My CORE 9L will sort of cowitness in the bottom of the RMR window. However the dot is slightly off from the front sight... both hit to POA I can't explain it. I ignore the sights and shoot the dot.

I too have Vortex Vipers on my COREs with no issues cowitnessing with iron sights