Removing serial is a lot harder these days bc the compression of stamping alters the metal and makes it hard, "filing off" does not work. Old guns maybe depending on how it was done, but new ones there is specific regulations (I think pressed to 0.003 inch?) so chemical etching will show different densities.

These days they can even catch over stamping, I heard about some cases using xray to do it. So it's more trouble than it's worth to remove serials on new guns usually. For some reason I hear about almost no instances of peening to hide it, which is probably because you need to know the right size and pressure so it mostly makes sense at scale.

It's funny the number of criminals that run around with literally filed off serials and get themselves literally 10x the time on the gun charge as whatever else they caught for.

You can instead get a shitty gun bc some have badly done serials (speshul wepunz has done this before, but ofc then you have to shoot one lol), you can get an old gun, you can finish an 80% lower. But most criminals just steal or straw buy, or buy smuggled guns (the philippines is notorious for this).