The SOLGW M4-EXO3 is a great entry level Complete AR-15 rifle that comes with all the features you want for a reliable, do-it-all carbine built for duty. This model features a 16" barrel machined from 4150 chrome moly vanadium steel and QPQ Nitride finished inside and out. The six groove 1/7 twist rate is optimal for heavy 62 grain 5.56 NATO surplus ammunition. The Mid-length gas system and appropriate gas port size ensures reliable function under any conditions and minimal recoil. The barrel is supported by the addition of the EXO3 Handguard that is M-Lok compatible that allows for adding a number of attachments