The thing is that the effectiveness of a weapon is partly based on size, and partly based on mass.
Lets take the simple example of a baseball bat. Hitting a 100 mph fastball with a bat, and getting a powerful hit with it are dependent on two things. Can you make contact, and if you can make contact, now much momentum will be transferred to the ball?
The baseball bats that players use have a regulated range of lengths and weights, amongst other regulations. Players choose the length and weight of their bats based on what suits them for their body size, strength, and hitting style. Professional fighters do the same things with their weapons. If you consider the same weapon types, shorter people tend to use shorter weapons. Stronger people tend to use heavier ones. Mix very short and very powerful physiques, and you end up with someone who can effectively use a very short, extremely heavy version of a human weapon.
I could very easily see dwarves making thick steel shells for maces, and melting lead into the form. If you haven't read them, I strongly suggest Gotrok & Felix warhammer based books. Darn good thinking materials when consisering what an extremely short, heavily muscled race would be able to do in melee combat. Just consider Gotrok an axelord.