In "The Survivors", Worf gives the following damage report:
Shields down! Captain, they hit us with four hundred gigawatts of particle energy!
From
here, the L/4.4 armour piercing shell as used by the SK C/34 guns of the
Hipper class cruisers has a mass of 122 kg, and a muzzle velocity of 925m/s. Using KE=0/5mv
2, each shell therefore has a KE of just over 52MJ.
The shell was 89.5cm long, and the impact time was therefore 9.68*10E-04 s. The power of a single shell's impact is therefore just under 53 GW. Each ship had 8 guns, so the power of a single broadside was, therefore, approximately 430GW - greater than the number Worf stated, and therefore sufficient to bring down the shields of a
Galaxy class starship.