▁as ▁a ▁backup ▁in ▁case ▁the ▁primary ▁lock ing ▁lug s ▁failed . ▁This ▁third ▁lug ▁is ▁a ▁distinct ive ▁feature ▁and ▁was ▁not ▁present ▁on ▁previous ▁M aus er ▁b olt ▁action ▁designs . ▁The ▁two ▁main ▁lock ing ▁lug s ▁display ▁a ▁lock ing ▁surface ▁of ▁ 5 6   mm ², ▁whilst ▁the ▁third ▁safety ▁lug ▁normally ▁plays ▁no ▁part ▁in ▁lock ing ▁the ▁action ▁to ▁avoid ▁asym metric ▁and ▁hence ▁un bal anced ▁b olt ▁thrust ▁forces . ▁The ▁diameter ▁of ▁the ▁receiver ▁was ▁also ▁en larg ed ▁compared ▁to ▁previous ▁M aus er ▁rece ivers ▁for ▁additional ▁strength ▁and ▁safety . ▁The ▁b olt ▁handle ▁is ▁perman ently ▁attached ▁to ▁the ▁b olt ▁and ▁on ▁the ▁M aus er ▁M ▁ 9 8 ▁series ▁is ▁turned - down ▁for ▁use ▁with ▁optical ▁s ights . ▁ ▁Another ▁distinct ive ▁feature ▁of ▁the ▁M ▁ 9 8 ▁system ▁is ▁the ▁controlled ▁round ▁feed ▁mechanism , ▁consisting ▁of ▁a ▁large , ▁non - rot ating ▁cla w ▁extract or ▁that ▁eng ages ▁the ▁cart ridge ▁case ▁rim ▁as ▁soon ▁as ▁the ▁round ▁leaves ▁the ▁magazine ▁and ▁firm ly ▁holds ▁the ▁cart ridge ▁case ▁until ▁the ▁round ▁is ▁e ject ed ▁by ▁the ▁e ject or , ▁mounted ▁inside ▁the ▁receiver . ▁Com b ined ▁with ▁a ▁slight ▁b olt ▁retra ction ▁at ▁the ▁last ▁stage ▁of ▁the ▁b olt ▁opening ▁cycle , ▁caused ▁by ▁the ▁cam med ▁surface ▁on ▁the ▁rear ▁receiver ▁bridge , ▁this ▁results ▁in ▁a ▁positive ▁cart