IIRC I based the 13.7mm shell weight on Warships1 data.
took 2 years and several blown-up guns to develop.
Who's to say a few Filipino guns won't go kablooie? Thanks for the story idea.
In that case, I reckon the data above is non-canonical. :-/ I was using either Warships1 shell weights, or the weights BG suggested for 'WWII' rounded up to the nearest 5 lbs.
RA - thanks for the warning on BG. I guess I'll just declare the data above to be 'non-canonical', and start from scratch.