It is a 7 round limit in New York, not 10.
they allow 10 round magazines.
you just are not allowed to load them with more than 7 rounds. this was changed shortly after the law went into effect as being totally unreasonable.
It is legal to buy and possess 10 round mags but under the unSAFE law, it is illegal to load them with more than 7 rounds unless you are at an incorporated shooting range.
Sound stupid? You are right! But this is an example of the idiocy of tyrants like Little Andy Cuomo.
FUAC
You are allowed to have a 10 round magazine, however you are only allowed to insert 7 rounds into them. The exception is at the range you can load all 10. Thus the restriction is 7 rounds in a 10 round magazine. A little known fact about NY is that CCW is determined by each individual county. Thus many counties upstate are shall issue for concealed carry, while downstate is mostly may issue(ie impossible).