umd0808
NES Member
As far as I know, such magazines are not illegal to possess in MA (Provided you have a large-capacity license). They are simply illegal to purchase or sell in MA. At least that's what I've gleaned from reading the MA statutes and listening to the salespeople at the S & W Store in Springfield.
Salespeople at S&W Store are grossly misinformed
http://northeastshooters.com/vbulletin/showthread.php?t=60307&highlight=high+cap+magazine
http://northeastshooters.com/vbulletin/showthread.php?t=58509&highlight=high+cap+magazine
http://northeastshooters.com/vbulletin/showthread.php?t=53589&highlight=high+cap+magazine