According to the historical marker on site (first link below) all equipment was sent to Selma after the take over, although no date is given.
I searched through the war years looking for ads for gunsmiths, etc, for the Arsenal, but was able to find none.
I did, however, locate the following (last two) ads, both of which were extensively re-printed in various papers. I'm sure that when Mr. Bryan reads your query, he will weigh in with some more factual material, and probably some of the other smart people of this board.
http://leepeacock2010.blogspot.com/2014/10/historical-marker-describes-old-mount.html
http://chroniclingamerica.loc.gov/lccn/sn84026536/1861-10-24/ed-1/seq-3/#date1=1836&sort=date&rows=20&words=Arsenal+Mount+Vernon&searchType=basic&sequence=0&index=3&state=&date2=1922&proxtext=%22Mount+Vernon+Arsenal%22&y=14&x=14&dateFilterType=yearRange&page=3
http://chroniclingamerica.loc.gov/lccn/sn84020712/1862-04-08/ed-1/seq-2/#date1=1836&sort=relevance&rows=20&words=Arsenal+Mount+Vernon&searchType=basic&sequence=0&index=14&state=&date2=1922&proxtext=%22Mount+Vernon+Arsenal%22&y=14&x=14&dateFilterType=yearRange&page=2
Regards,
Hoyt Cagle