A firearm with bolt assembly, the firearm comprising: a longitudinal axis (A-A); a receiver defining a longitudinally extending cavity; a barrel supported by the receiver and including a rear end and a front end; an ammunition magazine removably disposed in the receiver and including a pair of feed lips for retaining a plurality of cartridges in the magazine; and a rotatable bolt disposed in the cavity and slideably movable forward to a closed position in battery with the barrel and rearward to an open position axially spaced apart from the barrel, the bolt including: a bolt body including a front section, rear section, and middle section extending therebetween, the middle section comprising a dimensionally reduced portion of the bolt body having a smaller height and lateral width in transverse cross section than an outer diameter of the rear section; the middle section defining a downwardly and laterally open recess positioned over the feed lips of the magazine when the bolt is in the closed position, the recess receiving a portion of the feed lips therein; a bolt handle disposed on one side of the rear section; the middle section providing clearance between the bolt body and feed lips of the magazine when the bolt is in the closed position so that the bolt is rotatable between a locked breech position and unlocked breech position; characterized in that the bolt includes a plurality of bolt lugs selectively engageable with a plurality of locking lugs at the rear end of barrel, and in that the front section of the bolt body includes a downwardly extending projection which defines a bottom stub surface having a lateral width smaller than a lateral gap formed between the feed lips of the magazine, the stub surface being slideable forward and rearward between the feed lips. a longitudinal axis (A-A); a receiver defining a longitudinally extending cavity; a barrel supported by the receiver and including a rear end and a front end; an ammunition magazine removably disposed in the receiver and including a pair of feed lips for retaining a plurality of cartridges in the magazine; and a rotatable bolt disposed in the cavity and slideably movable forward to a closed position in battery with the barrel and rearward to an open position axially spaced apart from the barrel, the bolt including: a bolt body including a front section, rear section, and middle section extending therebetween, the middle section comprising a dimensionally reduced portion of the bolt body having a smaller height and lateral width in transverse cross section than an outer diameter of the rear section; the middle section defining a downwardly and laterally open recess positioned over the feed lips of the magazine when the bolt is in the closed position, the recess receiving a portion of the feed lips therein; a bolt handle disposed on one side of the rear section; a bolt body including a front section, rear section, and middle section extending therebetween, the middle section comprising a dimensionally reduced portion of the bolt body having a smaller height and lateral width in transverse cross section than an outer diameter of the rear section; the middle section defining a downwardly and laterally open recess positioned over the feed lips of the magazine when the bolt is in the closed position, the recess receiving a portion of the feed lips therein; a bolt handle disposed on one side of the rear section; the middle section providing clearance between the bolt body and feed lips of the magazine when the bolt is in the closed position so that the bolt is rotatable between a locked breech position and unlocked breech position; characterized in that the bolt includes a plurality of bolt lugs selectively engageable with a plurality of locking lugs at the rear end of barrel, and in that the front section of the bolt body includes a downwardly extending projection which defines a bottom stub surface having a lateral width smaller than a lateral gap formed between the feed lips of the magazine, the stub surface being slideable forward and rearward between the feed lips.