| CPC B25C 1/085 (2013.01) | 12 Claims |

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1. A fastener driving device comprising:
a combustion chamber;
a piston coupled to the combustion chamber and slidable within a sleeve such that combustion gas expansion in the combustion chamber causes the piston to slide from a first position to a second position;
a fastener channel configured to receive a fastener, wherein when moving from the first position to the second position, the piston is configured to engage the fastener and drive the fastener through the fastener channel and from the fastener driving device;
a first vent;
a return chamber configured to receive gas from the sleeve via the first vent;
a second vent coupled to the return chamber and configured to supply combustion gas from the combustion chamber to the return chamber; and
a nose leak channel configured to fluidly connect the return chamber to the fastener channel.
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