Quote Originally Posted by southchatham View Post
This advise will get you a felony.

No mags over 10 rounds. Pre-ban (prior to 98) mags over 10 are allowed. You must know which ones or face a felony.

The high capacity on your license is a MA thing and doesn't mean what other people think high capacity means. In other words, a revolver is not high capacity, and a Glock is.
Above is correct, other than the "magic date". Date for mags and "AWs" is 9/13/1994 - anything made on that date or earlier is legal. Anything made after that date (and that means the LE/Mil Only 9/13/1994 marked mags) is a 10 year felony in MA for possession regardless of any license you hold.

Quote Originally Posted by GreyGhost View Post
Do yourself a favor and only carry 10 round mags. That way you can't run afoul of any laws. State, county, or local. And yes they exist on all levels and they aren't always the same. BTW, I'm pretty sure Boston has some tighter regulations on capacity than the rest of the state.

In Mass you are required to take a class before you are issued a LTC of any kind. Your instructor should have gone over this with you in detail. The next time you go to Mass stop into a gun shop and ask if there's an instructor around. See if you can get some info from him. Normally I'd never suggest this but the gun owners in Mass are pretty good about helping each other out. And you live way too far from Mass to drop in and take a class.

Good luck and I hope you never have to defend yourself there. You will need deep pockets!
Best advice to carry 10 rd or less mags.

Sorry but gun shops and instructors are 99% horrible when it comes to MA gun laws! I ended up creating a 3 hour seminar on MA gun law (focused on how to stay out of jail/trouble . . . NOT the same as is required to get the LTC), to counter that mis-information with factual info. I teach it in Mansfield, MA and occasionally at Manchester Firing Line (Manchester, NH). Mass Firearms Detailed Class Information - Prices, Descriptions | RKBA

Ongoing best info on MA gun laws can be found here (in the MA gun laws subforum): Massachusetts Laws I pretty much "live there" in that subforum. These days I don't drop into DC except occasionally.