M16 Charging Handle

[SethB]

The Ljungman was nowhere near as refined as the Stoner system. In Stoner's system, the bolt is pushed forward by gas, unloading the bolt and rotating it at the same time. This is what makes such small lugs successful. Piston guns require a lot of work to keep the load even on the lugs.

[jtan163]

The Ljungman was nowhere near as refined as the Stoner system. In Stoner's system, the bolt is pushed forward by gas, unloading the bolt and rotating it at the same time. This is what makes such small lugs successful. Piston guns require a lot of work to keep the load even on the lugs.

I don't follow what you are saying - I thought that with most Stoner weapons - as with most, if not all, auto/semi auto small arms the bolt is pushed FORWARD (assuming the front is the muzzle, which I do) by a spring and backward via gas.

[SethB]

The weapon unlocks by pushing the bolt forward. This unloads the lugs. And it is why piston operated weapons have had issues with lug breakage in the past.

[Ken White]

Bolt CARRIER backwards -- but before the carrier moves, the gas flows in to the rear cavity and expands, pushing the bolt forward very slightly for a fraction of a second to unload the jugs and ease unlocking and rotation (caused by the beginning rearward movement of the bolt carrier camming the bolt counterclockwise). LINK.

The three little rings on the bolt (inside the red goose egg on the picture below...) are effectively piston rings to enable that.