Why are old grenades grooved while some are completely sleek?

The reason behind this change came from the fact that the grooves on the grenades did not work as expected by the inventor.

When thinking of the shape of a grenade, many people would think of images of grooves running along the grenade body. Of course it was the old grenade and they often had grooves along the body. At first glance they look like a pineapple.

Old grenades often have grooves along the body.

But in contrast to the current grenades, they no longer have grooves but instead are sleek designs. Why is there such a difference and what is the effect on the grenade?

Interestingly, grenades in the past did not have these grooves. The groove only appears after an improvement in the battle process. The soldiers originally built grenades from different objects such as a can and gunpowder. However, in 1915, William Mills, an engineer, an English inventor, invented a new, safer grenade with a manual detonator.

According to Technology, the use of this grenade is quite simple. You just need to pull the detonator to activate the grenade, then throw it at the enemy so that the impact of the explosion and the metal fragment can cause damage to the enemy. But contrary to that principle, grenades at that time were not the most lethal weapons. Because it is quite small and difficult to contain enough explosives that can increase the damage range.

Contradiction arises when the soldier needs small and light enough grenades to be able to carry with him when fighting. That means, a small grenade is hard to destroy a large number of enemy forces with just the default amount of explosives.

Mills devised a way to cut the grooves so that the grenade shell could easily split into sharp metal pieces.

The solution given now is to create another attack class for grenades. In particular, it caused the metal fragments to burst like bullets and damage the enemy as soon as the grenade exploded. Of course there are ways like adding sharp metal objects inside grenades, but Mills decided to use the body of a grenade as an attack weapon.

That's why Mills came up with a way to cut the grooves so that the grenade shell could easily split into sharp metal pieces that were hard to predict.

Grooved grenades do not fully maximize the desired effect

In 1918, the American Mk2 grenade appeared on the battlefield and it also had a deep groove, dividing the surface of the grenade into many squares. Many other countries later adopted this design solution.

But just a few decades later, people made a sleek body grenade? Why is there such a change?

The answer turned out to be very simple. Just because those grooves don't really work properly as expected. Mills found that grenades exploded and broke into pieces in random positions instead of exploding into square pieces.

The reason is that the cast iron layer is quite brittle. When exploded, they almost become iron powder under the pressure of the explosion and not enough to cause damage to the enemy. Only about a third of the grenade's body can become shrapnel and pose a danger.

Some grenades like the M26, M33 and M67 have completely smooth surfaces.

Even so, grooved grenades are still quite popular in some countries today. These grooves are also improved to become more compact and have better grip. There was even an improvement to create grooves inside the grenades, making it easier for debris to splash.

Some grenades like the M26, M33 and M67 have completely smooth surfaces. Besides, they are also considerably lighter than grooved grenades. Specifically, the new M67 grenade (speculum grenade) is about 200 grams lighter than the old MK2 but has a radius of up to 15m.

Thus, it can be understood that the improvement from groove grenade to sleek body is perfectly suited to combat requirements that require compactness but can still best promote the effectiveness of damage.