In 2025, the Springfield Kuna hit the market like wildfire. It is a well-designed, smooth-shooting, and compact PDW-style weapon. Chambered in 9mm, it has minimal recoil, and when suppressed, it goes from sexy to epic. A design feature that stands out on this handy little shooter is the action. Unlike what we are used to in our ARs, the Kuna uses a roller delayed system. Today, we will dive into this a bit and explain what it really is.
The Kuna Roller Delayed System – A Detailed Look
The roller-delayed blowback system uses two small rollers in the bolt assembly to delay the opening of the breech. Famously utilized in the Heckler & Koch MP5 and G3 rifles, this system provides a smooth shooting experience.
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The action works as follows. When the chamber is loaded, the bolt carrier forces a wedge-shaped locking piece forward. This forces two rollers outward into recesses in the barrel extension (trunnion), locking the bolt head in place. Once the round fires, chamber pressure pushes the casing back against the bolt head. This is where the magic of the delay takes place. The rollers, trapped in the trunnion, cannot move backward directly. Instead, they are forced inward against the angled surfaces of the locking piece.
The Delay
At that point, the angled surfaces act as a lever, forcing the bolt carrier and carrier assembly to move rearward at a much higher velocity than the bolt head. This process provides a significant delay, allowing the bullet to leave the barrel and the chamber pressure to drop to a safe level before the action unlocks. Once the rollers are fully retracted into the bolt head, the breech opens, and the spent case is ejected.
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Benefits
The benefits of this system are the ability to run higher-pressure rounds in small-frame firearms and reduced weight. It is also very reliable, which is why it is found in many submachine guns. One benefit that I am personally fond of is its friendliness toward suppressors. Because of the delayed opening, there is less “port pop” compared to direct blowback or direct impingement systems. All this, mixed with its reduced recoil, makes it a perfect action for the Kuna.
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The Kuna Roller Delayed System
It is rare for me to say this, but I am a fan boy of the Springfield Kuna. I have well over 2,000 rounds through it, and it just keeps getting better. The applications of this gun are many, but I personally believe it is an excellent PDW that works well in home defense or as a solid truck gun. If you have not yet had a chance to give one a spin, it needs to be on your list.
For more information, visit Springfield Armory.
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