MagBloks are inserted into the top of an empty magazine to so that the bolt lock does not lock the bolt to the rear when working the charging handle on semi-automatic rifles. This prevents the need to manually release the bolt each time it is racked when dry-fire training. The bolt will not lock back when MagBlok is inserted, causing the bolt to function as it would if the magazine had ammunition in it. This duplicates the mechanical functionality of your rifle when conducting dry-fire training, preventing unnecessary training scars! Each pack comes with three (3) MagBlok 556 inserts and are for rifles chambered in 5.56, .223 and 300 BLK only.
MagBloks should not be used without a RifleBlok properly inserted into your barrel.