In 2011, the Colorado Gun Collectors Association published an article entitled
Myths of the Blunderbuss, by Melvin Flanagan. The article was originally published in the
American Society of Arms Collectors Bulletin #96 September 2007.
In the article Mr. Flanagan takes on the assertion by noted weapons historian and author Harold L. Peterson, that the Pilgrims did not have blunderbusses, and that the blunderbuss' flared muzzle had very little effect on the dispersion of shot.
Mr. Flanagan also mentions a
“matchlock blunderbuss, traditionally thought to have been used in battle on the Zuiderzee in 1573, probably dates c.1600 and is in the Westfries Museum at Hoorn, no. K 31. A patent was granted to a Fenrick Theilmans of Echten on October 26, 1598 for a type of gun called a "Donderbus" that could be used on both land and sea and could shoot a pound of shot approximately 500 paces.”
The Colorado Gun Collectors Association host copies of the article here:
Part1:
http://www.cgca.com/Documents/2011May.pdf
Part2:
http://www.cgca.com/Documents/2011June.pdf