A voluntary registry is no registry.
Here's what you're looking at...
"...In other words, government officials cannot know that gun sales are being universally monitored unless they know the name of every gun owner and have identifying information about every gun possessed by those owners..."
The last gun I bought the FFL guy said the fed’s only keep the record for thirty days then they’re expunged; by law. Washington state keeps pistol purchases for sixty days and then are expunged; they’re two years behind in doing that.