Quoted:
I think you can register them via eFA-10.  As long as they are in a ban compliant configuration.

Federal Assault Weapons and Large Capacity Feeding Device Law as it existed prior to September 13, 2004
18 U.S.C.A.  921 This Federal law was repealed on September 13, 2004

921. Definitions
"The term 'semiautomatic assault weapon' means
(A) any of the firearms, or copies or duplicates of the firearms in any caliber, known as--
(i) Norinco, Mitchell, and Poly Technologies Avtomat Kalashnikovs (all models);
(ii) Action Arms Israeli Military Industries UZI and Galil;
(iii) Beretta Ar70 (SC-70);
(iv) Colt AR-15;
(v) Fabrique National FN/FAL, FN/LAR, and FNC;
(vi) SWD M-10, M-11, M-11/9, and M-12;
(vii) Steyr AUG;
(viii) INTRATEC TEC-9, TEC-DC9 and TEC-22; and
(ix) revolving cylinder shotguns, such as (or similar to) the Street Sweeper and Striker 12;
(B) a semiautomatic rifle that has an ability to accept a detachable magazine and has at least 2 of
(i) a folding or telescoping stock;
(ii) a pistol grip that protrudes conspicuously beneath the action of the weapon;
(iii) a bayonet mount;
(iv) a flash suppressor or threaded barrel designed to accommodate a flash suppressor; and
(v) a grenade launcher;
(C) a semiautomatic pistol that has an ability to accept a detachable magazine and has at least 2 of
(i) an ammunition magazine that attaches to the pistol outside of the pistol grip;
(ii) a threaded barrel capable of accepting a barrel extender, flash suppressor, forward handgrip, or silencer;
(iii) a shroud that is attached to, or partially or completely encircles, the barrel and that permits the shooter to hold the firearm with the nontrigger hand without being burned;
(iv) a manufactured weight of 50 ounces or more when the pistol is unloaded; and
(v) a semiautomatic version of an automatic firearm; and
(D) a semiautomatic shotgun that has at least 2 of--
(i) a folding or telescoping stock;
(ii) a pistol grip that protrudes conspicuously beneath the action of the weapon;
(iii) a fixed magazine capacity in excess of 5 rounds; and
(iv) an ability to accept a detachable magazine."

The term 'large capacity ammunition feeding device'
(A) means a magazine, belt, drum, feed strip, or similar device manufactured after the date of enactment of the Violent Crime Control and Law Enforcement Act of 1994 that has a capacity of, or that can be readily restored or converted to accept, more than 10 rounds of ammunition; but (B) does not include an attached tubular device designed to accept, and capable of operating only with, .22 caliber rimfire ammunition.

Quoted:
FYI - there is no requirement to "register" any of your previously-owned firearms when moving into MA since there has been no transfer (they were already yours).