slot 13 when magazine catch 10 is properly aligned the flat end 105 of the magazine catch 10 aligns with and is nested into slot 13 in the standard lower receiver 35 when a magazine 200 is installed in the magazine well 31 the protrusion 101 on the flat end 105 of the magazine catch 10 nests into the opening 202 of the magazine 200 and the edges of the protrusion 101 of the flat end 105 of the magazine catch 10 bears on the edges 203 of opening 202 of magazine 200 holding it firmly in place within the magazine well 31 referring to fig4 and 5 an alternative lower receiver 45 is shown for comparison with the standard lower receiver 35 this alternative lower receiver 45 is one embodiment of the lower receiver for the present invention the key difference visible in these two views is the presence of the hole 15 in the alternative lower receiver 45 in lieu of the slot 13 in the standard lower receiver 35 referring to fig4 and 7 the key difference visible in fig6 and 7 is the absence of the oval recess 122 present in face 123 of the standard lower receiver 35 but not present in face 124 of alternative lower receiver 45 as should be apparent the through hole 104 of fig4 as well as a recess counterbore not shown for the magazine catch spring 11 are also omitted in alternative lower receiver 45 referring to the exploded view.