I have a 725 Sporting. The trigger is held in place with a set screw. I wanted to change the position of the trigger but can't get the set screw loose. Tried 3 different allen wrenches (2mm) but now the screw is rounded out and still tight. I dressed down the wrenches with a file but no go. The gun is several years old with 1000s of rounds through it.
Thought about drilling out the screw which would be difficult . Any ideas?

Take it to a gunsmith would be my idea at the point you are at.

If it was mine, I would get a new trigger including the screw first, then drill out the old one and toss it. It may have been put in place with Lock Tite.

I got it handled but it was not fun. I had to cut the trigger into two pieces but it worked. I was not worried about saving the trigger as I had 5 more. I have two Brownings and each came with 3 triggers.. I took my time and watched carefully , there was no other damage to the gun. There is not a competent gunsmith for 150 miles from me.

Glad it worked out for you.

Next time try heating a steel rod to hear the set screw. Slowly does it.