The reasons why Heckler & Koch renamed the HK41 in 1974 are unclear. Part of their reasoning could have been that they wanted to change the perception of the rifle as being a semi-automatic sporting rifle instead of a paramilitary rifle. Furthermore, gun laws that were adopted in West Germany around that time prohibited the civilian ownership of paramilitary rifles. (As a side note, HK41s that were sold in West Germany came without flash suppressors because they were prohibited under the West German gun laws). As a result, Heckler & Koch modified the weapon with a plate welded inside the receiver to prevent the mounting of a full-auto "SEF" fire control group and re-designated the rifle as the Heckler & Koch HK91. Late pattern HK41s and HK91s are virtually identical in appearance (except for the receiver markings and the retaining hole of the cocking tube end cap) and all their parts are interchangeable. The last few HK91s that were delivered to the U.S. in 1989 were blocked by customs after President George H. W. Bush issued an Executive Order banning the importation of "non-sporting" rifles. These were slightly modified, to remove "non-sporting" features like the flash suppressor, and the receivers re-stamped as the HK911, forming a transitional model between the HK91 and the HK SR9.