Please see
http://www.omanisilver.com/contents/...Matchlock.html for a reasonable background on the weapon.
See also
https://books.google.com.om/books?id...chlock&f=false where Elgood discusses the more than likely appearance of Barrels other than European as well as from red sea sources as the pentagonal shape was preferred in Arabia.
The reference is further enhanced since Elgood worked and consulted on his fantastic book with the Tareq Rajeb Museum in Quwait which if you get the chance do go and see their amazing collections.