The cylinder holds the air the piston compresses. Match the cylinder volume to the inner barrel length, or your rifle either over-pressurises or wastes energy.

An AEG cylinder is the tube the piston travels inside. Its job is simple in principle — provide a sealed chamber for air compression on each shot — but its specifications matter more than most builders realise. The cylinder volume has to match the inner barrel length for the rifle to operate efficiently. Too much volume for the barrel length means wasted air and inconsistent FPS. Too little volume means the rifle can't generate full pressure and FPS drops.

Cylinder types correspond to barrel length ranges. Full-bore (type 0) cylinders are the longest, designed for 509mm+ inner barrels (DMR, sniper rifles, full-length M16s). Type 1 (port near the rear) cylinders suit 400-500mm barrels (carbines, longer M4s). Type 2 (port further forward) cylinders suit 300-400mm barrels (most CQB M4s). Type 3 ported cylinders are for short barrels (under 300mm, used in pistols and very short CQB builds). The port location lets air escape from the cylinder once the BB has passed a certain point in the barrel, preventing over-pressurisation.

Material and head considerations. Stainless steel cylinders are the durable standard — SHS, Lonex, Modify all stock these. Hardened aluminium cylinders are lighter and slightly more thermally conductive (less FPS variation in cold weather) — premium option. Cylinder heads (the front cap the piston seals against) are usually polymer or aluminium with an O-ring seal — replace these when O-rings wear. For pistons that cycle within these cylinders, see the dedicated collection. For inner barrels that need matching to cylinder volume, see the barrel collection.

💡 Titan Forge tip: If you're rebuilding a gearbox with a shorter inner barrel than stock (e.g. swapping a 363mm M4 barrel for a 247mm CQB barrel), match the cylinder to the new barrel length — otherwise FPS will plummet from over-volume waste. A £20 cylinder swap during a rebuild prevents a 50+ FPS drop and the resulting weak shot.