Break this into to jurisdictions, federal and state
Federal
You may purchase any C&R firearm from anyone, anywhere. You may purchase it in person in any state. You may have it shipped to you. Federal law is quite simple relative to your C&R. As long as the firearm is a C&R firearm and you have a C&R, you are good to go.
State (MA)
MA does not (yet) recognize your C&R license. Come 1/1/21 this will change. This means that inside MA the fact you have a C&R is not relevant. It gains you nothing. You have to abide by all state laws as if you did not have the C&R. FTF you do a eFA10. A dealer can sell you the C&R but is subject to the "list" for handguns. While you are out of state, federal law is in play (plus state law of the state you are in).
Come 1/1/21 MA recognizes the C&R in so much as a MA dealer can transfer to you even if off list.
Remember, however you acquire it, log into your bound book and also do your eFA10 within 7 days of acquisition (unless the method you got it had the seller doing the FA10)