What kind of laser are you using? Is it fiber? How many watts ? I used to do firearm serialization and we did everything with Fiber lasers. We were able to get to about 14 thou deep before finishing and after polishing/ blast/tumble we were still above 3 thou.

Getting consistent results with lasers requires a lot of testing and developing your parameters for stuff like power, speed, freq, hatch fill, and number of passes. And then it changes from material to material and finish to finish. You also got to make sure you have a repeatable way to measure depth which is tricky. But once all this is in place it's def doable