You will need to get a form 6 from the ATF (you can do it in your own name if it's a personal gun) before the gun hits customs. The UK exporter is likely to want to see that form before they can get an export permit. It takes 6-8 weeks to get the clearance from ATF. A licenced importer can do it faster (electronically). Then you need to get the gun shipped to you, c/o your local dealer is best. The customs broker will arrange this. You need to appoint a customs broker to clear it for you, and to ship it from the port of entry to your dealer. There will be brokerage fees, inland freight and duty to be paid. You could try to take possession in MA at the airport but that would probably be breaking a bunch of federal and state laws I am sure. In some states, you can legally buy or take possession of a gun in an adjoining state. I doubt MA is that tolerant.
I happen to be a licenced importer but if you are going to work with one, it's best to find one in your state of residence.
