Dutch guns

I have been doing some calculation about Dutch guns of bronze. In one case, a Dutch 24pdr gun was captured by the English. The gun was 9-1/2ft long and weighed some 4352 pounds. I estimate that a bronze 24pdr gun that weighed 4111 pounds was 9ft long. Going even further in estimating, I would estimate that a bronze 16pdr gun that weighed 3136 pounds was 9ft long. A bronze 16pdr gun that weighed 2961 pounds would be 8-1/2ft long. A bronze 15pdr that weighed 2761 pounds would be 8-1/4ft long. The only problem that I can see with these estimates is that they are probably wrong!