A weapon system for firing a round, comprising: a receiver; an operating group configured to operate the weapon system through a charged condition, a firing condition, and a recoil condition, the operating group comprising a barrel extension at least partially housed within the receiver and arranged to axially translate relative to the receiver; an operating rod (op-rod) assembly at least partially housed and arranged to axially translate within the barrel extension in the charge condition, the firing condition, and the recoil condition; and a bolt assembly coupled to the op-rod assembly and at least partially housed and arranged to axially translate within the barrel extension; a barrel coupled to the barrel extension and defining a chamber; a gas accelerator with a first end coupled to the barrel and a second end coupled to the op-rod assembly; a buffer assembly comprising a drive spring having a first end coupled to the receiver and a second end coupled to the op-rod assembly; and a lock assembly, wherein, in the charged condition, the op-rod assembly and the bolt assembly are retracted against the drive spring and the lock assembly is configured to secure the bolt assembly to the op-rod assembly; wherein, in the firing condition, the op-rod assembly and bolt assembly are driven by the drive spring such that the round is guided into the chamber and the op-rod assembly and bolt assembly are locked to the barrel extension and a forward momentum of the op-rod assembly is imparted to the operating group and the round is fired, wherein a portion of an impulse of the fired round stops the forward momentum of the operating group and the lock assembly is configured to release the bolt assembly from the op-rod assembly and the lock assembly is further configured to secure the bolt assembly to the barrel extension; wherein, in the recoil condition, the operating group is driven rearward by the remaining portion of the impulse of the fired round, the gas accelerator imparts additional rearward momentum to the op-rod assembly and bolt assembly and stops rearward momentum of the barrel and barrel extension, and the op-rod assembly and the bolt assembly are stopped by the drive spring. a receiver; an operating group configured to operate the weapon system through a charged condition, a firing condition, and a recoil condition, the operating group comprising a barrel extension at least partially housed within the receiver and arranged to axially translate relative to the receiver; an operating rod (op-rod) assembly at least partially housed and arranged to axially translate within the barrel extension in the charge condition, the firing condition, and the recoil condition; and a bolt assembly coupled to the op-rod assembly and at least partially housed and arranged to axially translate within the barrel extension; a barrel extension at least partially housed within the receiver and arranged to axially translate relative to the receiver; an operating rod (op-rod) assembly at least partially housed and arranged to axially translate within the barrel extension in the charge condition, the firing condition, and the recoil condition; and a bolt assembly coupled to the op-rod assembly and at least partially housed and arranged to axially translate within the barrel extension; a barrel coupled to the barrel extension and defining a chamber; a gas accelerator with a first end coupled to the barrel and a second end coupled to the op-rod assembly; a buffer assembly comprising a drive spring having a first end coupled to the receiver and a second end coupled to the op-rod assembly; and a lock assembly, wherein, in the charged condition, the op-rod assembly and the bolt assembly are retracted against the drive spring and the lock assembly is configured to secure the bolt assembly to the op-rod assembly; wherein, in the firing condition, the op-rod assembly and bolt assembly are driven by the drive spring such that the round is guided into the chamber and the op-rod assembly and bolt assembly are locked to the barrel extension and a forward momentum of the op-rod assembly is imparted to the operating group and the round is fired, wherein a portion of an impulse of the fired round stops the forward momentum of the operating group and the lock assembly is configured to release the bolt assembly from the op-rod assembly and the lock assembly is further configured to secure the bolt assembly to the barrel extension; wherein, in the recoil condition, the operating group is driven rearward by the remaining portion of the impulse of the fired round, the gas accelerator imparts additional rearward momentum to the op-rod assembly and bolt assembly and stops rearward momentum of the barrel and barrel extension, and the op-rod assembly and the bolt assembly are stopped by the drive spring. the operating group is driven rearward by the remaining portion of the impulse of the fired round, the gas accelerator imparts additional rearward momentum to the op-rod assembly and bolt assembly and stops rearward momentum of the barrel and barrel extension, and the op-rod assembly and the bolt assembly are stopped by the drive spring.