Tumble Upon Impact (TUI) Ammunition: A Comprehensive Analysis

For those with a keen interest in firearms and ammunition, the innovative design of Fort Scott’s Tumble Upon Impact (TUI) ammunition is significant. This style of ammo is not just another bullet, but a game-changer in the ballistic performance realm. Here at KIR Ammo, we endeavor to provide insights into this type of ammunition, comparing it with similar ammunition that came before it, and discussing its implications in contemporary shooting practices.

Tumble Upon Impact Ammunition

What is Tumble Upon Impact Ammunition?

Fort Scott’s TUI ammunition, as the name suggests, is designed to tumble upon impact, thereby maximizing the damage to the target. The tumbling feature of this ammunition type is available in both rifle ammunition and pistol ammunition. This unique behavior results from the precisely engineered geometry of the bullet, a characteristic that sets it apart from traditional ammunition. These bullets are produced through a meticulous manufacturing process, ensuring high-quality performance and consistent results across different types of TUI rounds, whether they’re designed for hunting, self-defense, or professional use. This concept of TUI, however, it not necessarily unique as 5.56x45mm ammo also inherently tumbles upon impact.  Like some of its predecessors, TUI ammunition is intended to disable a target with the aforementioned tumbling effect.  Theoretically, this tumbling motion could make a projectile enter the chest cavity and exit a different part of the body altogether.  However, testing of TUI ammo doesn’t always yield this type of result.  The following video outlines some interesting performance details on tumbling ammunition vs. FMJ 9mm.

Are Bullet Designed to Tumble?
The concept of bullets tumbling, also known as bullet yaw, is often misunderstood. Bullets are not designed to tumble in flight; they are engineered to fly straight and true toward the target for maximum accuracy. However, upon impact, certain bullet designs, particularly those used in military applications like the 5.56 NATO, may exhibit tumbling behavior due to their center of mass and velocity, which can create a larger wound channel. This effect is often a byproduct of the bullet’s interaction with the target rather than an intentional design feature. The stability of a bullet in flight is determined by its design, including factors such as the bullet’s shape, the center of gravity, and the rifling of the barrel from which it is fired.

TUI Ammunition Informational Video

The History of Tumbling Ammo:

Tumbling ammunition, or more specifically the concept of bullet tumbling, has been a point of interest in the field of ballistics for quite some time. The phenomenon has both intentional and unintentional manifestations and has been exploited in various ways over the history of firearms development.

  1. Early Observations and Unintentional Tumbling:

The concept of bullet tumbling was first observed unintentionally in early firearms. As smoothbore muskets evolved into rifled firearms in the 19th century, gunsmiths noticed that bullets didn’t always fly straight and true – sometimes they’d tumble, or flip end-over-end, upon exiting the barrel or striking a target. While rifling was supposed to impart a stabilizing spin on the bullet, imperfect manufacturing techniques, combined with sub-optimal bullet designs, often led to this unintended tumbling.

  1. Advent of Spitzer Bullets:

The late 19th and early 20th century saw the adoption of ‘spitzer’ (pointed) bullets, which had a more aerodynamic shape compared to the round-nosed bullets of the past. These spitzer bullets, when combined with a fast rifling twist, generally stabilized better and were less prone to unintentional tumbling. However, they could still tumble upon hitting a target, causing a more severe wound than a non-tumbling bullet, an effect that was observed in military and hunting contexts.

  1. Intentional Tumbling:

The late 20th century saw interest in intentionally designing ammunition to tumble upon impact. The rationale behind this design was to maximize the damage to a soft target. The best-known example is the 5.56mm M193 round used by the US military in the early days of the M16 rifle. These bullets were lightweight and traveled at high velocity, and under certain conditions, they’d tumble and fragment upon hitting a target, causing a significant wound.

  1. Modern TUI Ammunition:

More recently, specific types of ammunition, like Tumble Upon Impact (TUI) rounds, have been designed to exploit the tumbling effect to the fullest. The bullets in these rounds are specifically engineered to tumble upon hitting a target, maximizing the energy transfer and creating a large wound channel.

Ballistic Performance of TUI Ammunition:

One of the striking features of Fort Scott’s TUI ammo is its impressive ballistic performance. Its tumbling effect upon impact does theoretically lead to a significantly larger wound channel, creating a more incapacitating effect than conventional rounds. This makes TUI ammo particularly effective for self-defense and law enforcement situations where stopping the threat swiftly is crucial. However, it’s worth noting that while TUI ammunition outperforms traditional rounds in specific scenarios, it may not be the best choice for every situation. It is also important to keep in mind that every pistol will distribute these projectiles differently based on the specific build of the firearm.  It is important to practice with your firearm should you choose to use a tumbling projectile.

What is the Difference Between Tumbling Ammo and Hollow Point Ammo?

The main difference between tumbling ammunition and other ammunitions that change upon impact (like a hollow point) is that tumbling ammunition disperses the the kinetic energy through the tumbling effect without a significant metamorphosis of the projectile.  Therefore, unlike the “mushrooming” effect of a hollow point or the fractioning effect of a frangible ammo, the projectile stays relatively unchanged while tumbling through the target. The result of the tumbling is evident when testing the ammo in ballistic gel as the wound cavity is typically significantly larger than hollow point rounds.

Tactical Applications of TUI Ammunition:

The effective use of TUI ammunition spans across various fields. Law enforcement agencies appreciate its immediate stopping power, reducing the risk to bystanders. Military personnel find its incapacitating effects valuable in warfare scenarios and this type of ammo has been used in warfare for decades. Civilians too, particularly those concerned with personal defense, recognize the advantages of TUI rounds.

Similar Ammunition Types:

Several other ammunition types share some characteristics with TUI ammo, in that, these ammunitions are designed to do more damage upon impact. Hollow point bullets and frangible ammunition are some examples. Hollow points, designed to expand upon impact, and frangible bullets, which break apart when they hit the target, have their own merits and drawbacks in comparison to TUI rounds.  The choice of ammunition depends on the specific requirements of the user and the use-case for the ammo.

Future of TUI Ammunition:

The future looks bright for tumbling ammunition as it has a significant place in modern warfare, hunting, and personal projection. With technological advancements on the horizon promising to further enhance bullet performance, it is likely that this type of ammunition will continue to be desirable. The ever-changing landscape of warfare tactics also continues to shape the development and use of such ammunition. It will be interesting to see how Fort Scott’s TUI and its counterparts evolve to meet these emerging needs.

Can You Hunt with Tumble Upon Impact Ammunition?
Yes. Recoil is light without sacrificing the velocity you need for hunting game at medium to longer distances.


Tumbling ammunition did have a part in revolutionizing the ammunition landscape at one time. With its unique design and superior damage capabilities, we don’t expect it will be going away any time soon. While it is not the ultimate solution for all shooting scenarios, it offers significant advantages in specific contexts. By understanding its properties, users can make an informed decision to best suit their needs.

At KIR Ammo, we’re dedicated to providing top-quality ammunition products, including a range of TUI rounds. We’re here to help you make the best ammunition choice for your needs. Explore our selection today!

Our Most Popular TUI Ammunition

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