NBU Ribbed Cylinder – Ported (200–400 mm)

AirsoftParts NBU Ported Cylinder for Bore Up Air Seal Systems
The manufacturer recommends this version for barrels up to 400 mm, with a more specific recommended range of 200–400 mm and M4 or MP5 as typical examples. The port in the cylinder wall causes effective compression to begin only after it is covered by the piston, so the cylinder uses a smaller portion of its total volume than the full NBU version. Due to the enlarged diameter, the cylinder must be combined with a corresponding NBU piston head and NBU cylinder head; standard versions of these components are not designed for it. The cylinder is made of stainless steel, and the polished inner surface provides a smooth, low-friction working surface for the piston head seals. The manufacturer also specifies concentric machining. The cylinder weighs 25.1 g, has no external cooling grooves, is designed for V2 and V3 gearboxes with the corresponding NBU air seal system, and the maximum recommended spring is M170.
Key Features

NBU / Bore Up Design
The enlarged 24.7 mm inner diameter provides a larger cross-section than a standard cylinder and corresponds to the dimensions of NBU / Bore Up air seal systems.

Ported Cylinder for Shorter Barrels
The port in the cylinder wall adjusts the usable air volume, and the manufacturer recommends this version for 200–400 mm inner barrels, such as various M4 or MP5 configurations.

Polished Stainless Steel Surface
The cylinder is made of stainless steel with a polished surface, providing a smooth working surface and reducing friction of the sealing elements as the piston head moves.

Requires NBU Components
Due to the 24.7 mm inner diameter, the cylinder m..