Japanese bombs
 

Can some one tell me if the Japanese used a small bomb no more than a foot long and a few pounds in weight, it looks similar to a rifle grenade and was built around that design...but was definately for air use i think ??

I am sure the Zero carried it for dropping on troops , airfields etc...

Re: Japanese bombs
 

The Zero could carry two 30kg bombs under its wings. These were about 33 inches long and were used for ground attack. Modified versions were used for air-air bombing. It could also carry 60kg bombs. Later the Zero was modified to carry a 250kg bomb under the fuselage. None of these fits the description of the bomb you describe.

RLD