Some of them could get to two rounds per minute or so. 2 problems being that many of them loaded at a fixed angle like 5 degrees so at long range the guns had to lowered to load and elevated back to firing position which slowed the rate of fire.
2nd problem combines, I think, with the accuracy question. At the longer ranges the time of flight was longer than the loading cycle, so if you fired at max rate of fire you were firing without knowing were the last salvo landed.
Also the guns were fired at a certain point in the ships roll. they did not try to elevate or depress the guns to compensate for the roll. This could also affect the rate of fire.
Battleship main guns typically fired at long range. When firing @ 20,000 yards you spot shell spashes and then adjust to (hopefully) put salvos on target. A slow business. 1 salvo per minute was more or less common.
Point blank night battles within effective torpedo range work differently. For such fights the cyclic rate matters. It's crucial to break up an enemy destroyer charge before they launch torpedoes. Cruisers armed with rapid fire 6" main guns such as the USN Cleveland class and German Königsberg class were especially useful in such knife fights.