to the standard bolt housing which it replaces the bolt housing 15 has a breech opening 20 and a barrel receiving area 21 seen in fig1 of the drawings a pair of rails 22 and 23 are formed in the housing adjacent to the recessed area 21 and have locking notches 24 and 25 within which are engageable by a sear 26 in the trigger assembly 14 an elongated spring receptacle bore 27 extends longitudinally the length of the housing 16 above and to the right when viewed in cross section of said barrel receiving area 21 a recessed area 28 is formed in the uppermost surface of the housing 15 and has a pair of spaced vertically aligned apertures a within intersecting the barrel receiving area 21 best seen in fig2 of the drawings the striker bolt 16 can be seen in fig2 and 4 and inverted in fig8 of the drawings and is comprised of a generally rectangular main body member 29 having a round upstanding end portion 30 and a cutaway multiple configured portion 31 a bore 32 extends on an axial centered plane through said end and configured portions 30 and 31 respectively with an area of increased interior dimension at 33 within the end portion 30 a slot 34 is formed horizontally in the side of the end portion 30 intersecting said area of increased dimension at 33 a secondary slot 35 defines a recessed area in the top surface of said end portion and again intersects said area of increased diameter at 33 just below the multi configured.