I recently bought myself a new smith and Wesson m&p 500 in a .223/5.56 nato and was wondering if there is way to put a scope on while still having the open sights. I would be willing to buy a night vision scope with a spot for a reflex sight also because it seems to be easier to shoot with both eyes open and with a relex of red dot sight. The main idea I'm gonna use this for is just putting out lots of rounds against hogs.

You could throw some irons or a red dot at 45 degrees.

QD Scope mount and a good pair of BUIS.

Just buy a 1-4x and use it on the lowest magnification both eyes open.

Yup. I put a 1-6X on mine and couldn't be happier.

Aimpoint patrol optic.

This! The only way to run a 1-4 with BUIS is run the butt stock collapsed and chin in the charging handle in order to get the scope far enough forward to clear the BUIS.

Just use higher rings and you won't have to play that game.

Go scope, or irons on top of the rifle, not both. If the scope breaks down have the rear iron sight in the case the rifle rides in. At least that's what I do.

You also can do the 45 degree offset iron sights. XS sights and someone else makes them.

Can you buy high scope mounts to have both iron sights and a scope?

You can, but I wouldn't recommend it. You'll have one cheek weld for the irons, and a different one for the scope. I've tried it on a .22 lr as well as an AR, didn't work very well either time. The 1-6X scope gives the best of both worlds with a constant proper cheek weld.

I know someone that has it on their Winchester 30-30 and they love it, iron at 50 yards and scope at 200 yards. Don't think that would work well for an at-15 though