LITTLE KNOWN FACTS ABOUT P80 GLOCK FOR SALE.

I'm baffled. I purchased a 22lr revolver a few weeks back, I desired to lengthen the barrel by about 2 inches so I asked in which I could purchase a alternative barrel on the manufactures Web-site, they mentioned the gun was registered to me from the atf with a specific barrel size and when I change that I would need a new serial variety.Complete t