RMCX-300B-5B-TAP-SBR View cart “Sig MCX Rattler SBR 300 Blackout, 5.5″, Minimalist Stock, Alum M-LOK HG, 1x30rd All NFA Rules Apply” has been added to your cart. Showing the single result Default sorting Sort by popularity Sort by average rating Sort by latest Sort by price: low to high Sort by price: high to low Sale! IN STOCKSig MCX Rattler SBR 300 Blackout, 5.5″, Minimalist Stock, Alum M-LOK HG, 1x30rd All NFA Rules Apply $2,499.99 Original price was: $2,499.99.$2,249.99Current price is: $2,249.99. Add to cart