"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.