FIG. 1 is a top rear left isometric view of a firearm lower receiver showing the new design;
FIG. 2 is a bottom front left isometric view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a top rear right isometric view thereof;
FIG. 5 is a bottom front right isometric view thereof;
FIG. 6 is a right side view thereof;
FIG. 7 is a rear view thereof;
FIG. 8 is a front view thereof;
FIG. 9 is a top view thereof;
FIG. 10 is a bottom view thereof;
FIG. 11 is an enlarged detailed view of FIG. 2; and,
FIG. 12 is an enlarged detailed view of FIG. 4.
The evenly spaced broken lines and the unshaded areas adjacent to them depict portions of the firearm lower receiver that form no part of the claimed design. The dot-dot-dash broken lines depict the boundaries of the enlargements that form no part of the claimed design.