The ornamental design for a six-sided handrail for firearms, as shown and described.
FIG. 1 is a perspective view of the six-sided handrail for firearms in accordance with my invention;
FIG. 2 is a front end view thereof, taken from the right side of FIG. 1;
FIG. 3 is a back end view thereof, taken from the left side of FIG. 1;
FIG. 4 is a first side view thereof;
FIG. 5 is a second side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
Broken lines shown in FIGS. 1, 3, and 7 are included for the purpose of illustrating a portion of the six-sided handrail for firearms that forms no part of the claimed design. The surface indicia of parallel lines also form no part of the claimed design and are merely surface shading.