Inline blowback (paintball)

An inline blowback is a type of blowback design. A blowback marker is one that when the trigger is pulled, the sear is released, which allows the striker, which is linked to the bolt, to slam into the valve, which releases air into the bolt, which is redirected out the barrel. The valve also releases air back into the striker, pushing it back and recocking the marker. 
An inline blowback is where the bolt, striker, and valve are all adjacent horizontally in the same tube, instead of in a stacked tube blowback where the valve and striker are in one tube, and the bolt is in another tube above the valve and striker.
The blowback design in general is the most affordable way of making a semi automatic paintball marker, that doesn't need the use of compressed air/nitrogen or any type of regulation on gas.
Operation.
The operation of an inline blowback marker can be separated into four stages:
Ideally, the firing stage will complete before the feed tube is reopened. This prevents gas from venting out the tube instead of propelling the ball, which would require a greater volume of gas to bring the ball to the correct velocity. However, this is not the sign of a sloppy marker, as a slight pressure on the paintballs in the feed tube can help "unjam" standard gravity-fed hoppers. Some of the most common inline blowback markers are made by Tippmann.
Basic troubleshooting.
Some inline blowback markers will leak air from the barrel when uncocked. The striker sits forward against the seal pin, causing the cup seal to open enough to leak air from the valve, which escapes out the barrel. Pull the charging handle or knob to pull back the striker and remove the pressure from the seal pin. However, during storage, you should always remove the air source and leave the marker uncocked. The rear spring can be damaged if stored a long time in a cocked position.