How many grandslams home runs hit in NY Mets history?

There are on between 14 thru 19 Gramd Slams produced on every year in MLB.T.Ahlgren

Actually, according to MLB.com, here are the number of grand slams for the years 1999-2008:

So, it usually averages about 130 per year between all 30 major league teams.

1999140200017620011342002125200312320041332005132200613220071342008124