I know that, but I like many I know do NOT shoot at “regulated” ranges.
I don’t like shooting where it’s regulated. Just like only one of my firearms is registered and has a serial number - the others are not and do not but are fully legal.
Not everybody lives in the sticks. Some of us live in the cities where an indoor range is within a half hours or hours drive, while an unregulated range may be hours away. I am not going to make shooting an all day proposition just because I don’t have the benefit of shooting off my back porch or have a public range without a range master.
So, you’re saying “All but ONE of your firearms doesn’t have a serial number?”