Ar 15 Drop In Auto Sear

10 TURNS NO. 18 MUSIC WIRE RAT E 8 lbs in The trip pin can be made from drill rod stock. Although I find a roll pin works as well without the need for a precision fit in the sear housing. Whichever is used, make sure the trip rocks freely on the pin when it's assembled. Test fire as outlined at the end of CHAPTER ONE.