"Generally accepted" on two points---the gun's maker (Boss) and seller (Wicks)---is surely subordinate to the authorized biography, seven years of scholarly work by a distinguished writer, academic and friend.
"He chose a double-barreled Boss shotgun with a tight choke."
Specificity at this delicate juncture, authorized by EH's family and trustees, carries more weight than the contents of A&F records and the celebrated sceptical musings of Montaigne.
King:
But what about the shotgun artifacts shown in an earlier post held by the firm that purportedly destroyed the gun? They do not appear to me to be from a Boss shotgun. I always look for a motive when tracing someting like this story and who whould be motivated to fake fragments from a destroyed suicide gun and to what end?
Jim