Is the Cobra 80 fire cracker "three to four times as powerful" as a hand grenade?

Question

In this news article about illegal fireworks it is claimed (translated from Dutch):

Chief of police Oscar Dros of the Oost-Nederland police district says that fireworks is no longer innocent. "We recently found a stash of illegal fireworks in Arnhem containing Cobra 80s. I wouldn't call that a firecracker, but an assault grenade."

According to the police chief a Cobra 80 is three to four times as powerful as a real hand grenade.

Is this accurate?

It doesn't specify which "real hand grenade" the Cobra 80 is being compared against, but any commonly used modern real (i.e. non-practice) hand grenade would be reasonable.

Answer 1

This post on a Dutch IT forum may shed some light on this matter. This guy seems to access to some facts about the M67 hand grenade, as well as the Cobra 6 [not Cobra 80] firework:

De M67 hand granaat die op dit moment gebruikt wordt door verschillende landen (waaronder de US) heeft een kruit inhoud van 180 gram. Dat kruit bestaat uit 39.4% TNT en 59.5% RDX. Deze hebben een omrekeningsfactor van 1.1 en 1.5.

The M67 hand grenade, currently widely used (also in the US) has an explosive content of 180 grams. this is 39.4% TNT and 59.5% RDX. They have TNT-equivalence factors of 1.1 and 1.5 respectively.

Flashkruit wat in vuurwerk knallers gebruikt wordt heeft een omrekeningsfactor van 0.45. Een Cobra 6 bevat 48.5 gram kruit waarvan 28.5 gram flash voor de knal, de rest van het kruit is voor de vlam voorafgaand aan de knal.

Flash powder in fireworks has a TNT-equivalence factor of 0.45. A Cobra 6 contans 48.5 grams of explosive, of which only 28.5 grams is used for the actual bang. The rest of the powder is for a big flame before the bang.

So now we start calculating:

180/28.5 = een handgranaat bevat 6.3 keer zoveel kruit als een Cobra 6. Waarvan dan ook nog 39.4% van de inhoud van de handgranaat 1.1/0.45 = 2.44 keer zo krachtig is als een Cobra 6. En 59.5% van de inhoud van de handgranaat 1.5/0.45 = 3.33 keer zo krachtig is als een Cobra 6. Daarnaast bestaat de huls van de Cobra 6 uit uit karton en 2 plastic dopjes. De huls van een handgranaat bestaat uit metaal.

A hand grenade contains 180/28.5 = 6.3 times as much explosive than a Cobra 6. 39.4% of that is 1.1/0.45 = 2.44 times more explosive than the Cobra 6 powder, and 59.5% is 1.5/0.45 = 3.33 times as powerful. Finally, the Cobra is covered in cardboard and two pieces of plastic - the hand grenade is covered in metal.

Now, some very quick calculations show that according to this data, an M67 hand grenade is at least 8.3 times more powerful than a Cobra 6.

Thanks to the link provided by @jjack I see there is a Cobra 80, as can be seen on this page

It specifies there is 250 grams of flash powder in it. Now, even assuming that all of that is used for the bang (although this youtube video seems to show at least some of the explosive is used to launch the thing...), we would get a TNT equivalent of 0.45*250 = 112.5 grams of TNT.

The hand grenade is still more powerful with the equivalent of 238 grams of TNT.

So while that Cobra 80 seems indeed a dangerous piece of fireworks, it's not even half as powerful as a hand grenade, even if we still ignore the difference in packaging (plastic versus metal).

Answer 2

The Netherlands produced for decades a small grenade, the V40. This was a defensively used fragmentation grenade, although the smaller radius and grenade size is usually associated with offensively-used fragmentation grenade.^note

With a total mass of 136 grams, its golf-ball sized spherical sleeve was made from notched steel, containing about 36g of Composition B which is about 42g of TNT equivalent, which means this hand grenade is 2-3 times less 'powerful' than the Cobra 80 (112g TNT equivalent).

A final consideration is that for the "explosion power" the scale is logarithmic (as sound intensity and similar quantities, see pag.7 of the US Army technical report NATICK/TR-95/003 "Blast overpressure and survivability calculations for various sizes of explosive charges") , therefore thing A being 3-4 times more powerful than B is probably not that relevant. The difference when it explodes in your hand is negligible, the effects are catastrophic.

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Note: the defensive term associated with the frag-grenade in the wiki is debated (and rightly so, as anyone that did basic infantry training would know):

Fragmentation grenades can be divided into two main types, defensive and offensive, where the former are designed to be used from a position of cover (e.g. in a slit trench or behind a suitable wall) against an open area outside, and have an effective kill radius greater than the distance they can be thrown; while the latter are for use by assaulting troops, and have a smaller effective radius.
—"Grenade", Wikipedia