Picked up a P320 professional the other day and I finally got my leupold DPP in today. Figured piece of cake two screw out to get the plate off and two screws in to attach the DPP.

Well...

Sig must of used some industrial strength thread locker because I couldn’t get the screws to budge. Tried heating them but they both stripped. EZ out broke in one of them. I drilled the heads off and was going to try and use pliers to turn them out. However, they are still locked in there and not enough material to grab them with locking pliers anyway.

What’s my best next step?

gunsmith or machine shop  -----drill and tap

Drill out using a center bit to start the hole.

I'd highly recommend they be faced flat with an end mill first so the center drill doesn't want to walk off it.

Then drill them with a left hand drill bit. Should come right out.

Thanks for the replies. Researched my options and I think I’ve screwed this up enough and will find a pro.

Never seen a center drill walk.
They have almost no length and if the setup is solid
you can even start on a round object or off perpendicular.

This is the way to do it, if you have access to a mill.

If not, use a thin file to create a slot for a flathead screwdriver. Soak them in Kroil overnight. Then apply heat with an oxy-acetylene torch and try unscrewing them carefully (with lots of downward pressure).

"Oxy-acetylene"  is overkill.
Air-acetylene is hot enough.