Bundle.

This is coolbert:

The Germans had this figured out over one-hundred years ago! 

"Like Legos: Navy wants stackable grenades to create larger explosions"

"Several new types of grenades, including one that can be stacked to create a larger explosion, have garnered interest from the Department of the Navy."

Thanks to Stars and Stripes for the tip.

"The Crane, Ind.-based Naval Surface Warfare Center issued a request for information about the modular grenades last month, along with several other early-stage procurement notices about several flash-bang grenade variants. The Marine Corps also has expressed interest in the stacking grenades."

AS TO THE GERMAN USE OF "STACKED GRENADES" FROM THE WW1 ERA CONSIDER:

"Improvised 'bundle charge'". Stielhandgranate bundle."

"To counter the lack of effectiveness against hard targets such as tanks and buildings, a common solution was created in the form of an improvised 'bundle charge'. The charges of a number of M24 grenades – their handles and fuses removed – would be strapped around a complete grenade, usually with simple rope, cloth, or metal wire. These could be crafted with up to six additional charges, and in battle the most common styles to see were the addition of four or six. Unofficially, these improvised bundle grenades were known as Geballte Ladung " 

"As a result of this cost-effective and reliable solution, the standard infantryman of the Wehrmacht  [and the stormtrooper of the WW1 era before that] could quickly improvise a grenade with up to seven times the explosive power. However, the added weight made it more difficult to throw, and the increased size meant that it was not practical to carry with one hand and that far fewer could be carried. These factors meant that infantry squads, if faced with an armored enemy, would have to close to a reduced range if they wanted to use the bundle charges."

Just gotta be careful so some soldier does not create a bundled grenade of such size he blows himself up in the process upon detonation.

coolbert.