gaw[25] - cannon

El Galeon is armed with 20 cast-iron cannon, a mixture of demi-culverin and demi-cannon. Plus a number of Swivel guns, which mount onto the gunwale [usually on the poop deck or forecastle]. This one is lashed up in a manner similar to the method required when "on passage".
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For information ...

a demi-culverin has a 4" bore, firing an 8 - 10lb ball - each shot requires 6lb of black [gun-] powder
a demi-cannon has a 6" bore, firing a 32lb ball - each shot needs 18lb of powder.
Accuracy drops off dramatically at longer ranges, the smaller culverin had a range of about 1,800ft.
[depending on the target, solid balls could be replaced by canister [ie shrapnel], chain or bar shot].
The heavier guns required a larger number of men to work them.