– SIG SAUER M400 Tread 5.56 NATO – 223 Remington Designed and built to be a solid weapon for beginners to experts, the SIG M400 Tread rifle has the features you need at a price that fits your budget. Buy Sig Sauer M400. The 5.56 NATO Sig Sauer M400 Tread comes with one 30-roun...