The Colt 1902 Military
"Browning's idea was to make the barrel free to move somewhat, unlike in the straight blowback design, and anchor it to the frame by means of a pair of swinging links, one at the rear of the barrel and one at the front. On firing, the whole assemblage of barrel and slide would move rearward locked together by means of lugs machined atop the barrel that fitted into mortises in the underside of the slide. This would only be for a short distance, as the links would naturally pivot about their pins, causing the barrel to drop down and unlock from the slide."Tam has written an incisive article on the Colt 1902. Read more about the forerunner to the 1911 here.