USPSA - Tonto Rim Sports Club - Payson, AZ Excitement About USPSA: Books, Biography, Blog, Audiobooks, Kindle 69 inches), USPSA Open altered the maximum magazine length from 170 mm to 171. 25 mm (6. 742 inches) someplace between 2004 and 2009. [] Confusingly, some 171. 25 mm magazine setups are marketed