[Jeff Head]

Excellent find on the documentation of what several of us have tried to say in our own words. Thanks.

[SauronOfMordor]

I went looking for the higher-calibre guns that GreyFriar mentioned. The Italian 76mm fires a bigger projectile (14 lbs vs 6 lbs), but at a lower rate of fire (120 rpm vs 220), and per the article, has

reliability and accuracy problems. When fired at maximum ROF, there is a tendency for the mount to "self-destruct," in the words of one of the Project Engineers who worked on the weapon. During a test shoot, the weapon was unable to hold a 20-round burst on a 20 x 20 foot (6m x 6m) target at 500 yards (460 m).

The Italian 127mm can only do 40 rpm of much heavier rounds (67 lbs avg)

The 57mm's high rate of fire will put a comparable amount of HE on target, and is likely to be more effective against swarm attacks of lots of small expendable boats.

Realisticly, anything that needs hitting with a 127mm is worth hitting with a missile