heavy ships were:
UTAH Bombardment Group
Bombardment GroupRear Adm. M. L. Deyo, USN
USS Tuscaloosa(flagship) (CA)Capt. J. B. W. Waller,
USN USS Nevada(battleship)Capt. P. M. Rhea, USN
USS Quincy (heavy cruiser)Capt. E. M. Senn, USN
*HMS Erebus(monitor)Capt. J. S. P. Colquhoun, RN
HMS Hawkins(heavy cruiser)Capt. J. W. Josselyn, D.S.C., RN
HMS Black Prince(light cruiser)Capt. D. M. Lees, D.S.O., RN
HMS Enterprise(light cruiser)Capt. H. T. W. Grant, D.S.O., RCN
*HMNS SoembaLtCdr. H. H. L. Propper, RNN
*Joined in the battle area because of slow speed
Of these, the venerable Nevada was by far the most powerful with her ten 14" guns, sixteen 5" and up-to-date fire control equipment. Her lack of speed was no handicap in this assignment. Quincy was next, a new ship with nine 8", twelve 5" and everything modern. Tuscaloosa, a useful cruiser of nine 8", eight 5", eleven years old, and not the latest equipment. Of the British cruisers the Hawkins fitted with seven 7.5" and nine 4" guns but she was old. The others were smaller gunned ships. Black Prince was new but only eight 5.25" guns; Enterprise 6" but already due for decommissioning. Erebus boasted two 15" guns. She too was ancient and her accuracy of fire was questionable. Soemba was 19 years old, a gunboat with three 5.9" guns.
The OMAHA Group heavy ships were:
Bombardment Group CommanderRear Adm. C. F. Bryant, USN
USS Texas (flagship) (Old BB)Capt. C. A. Baker, USN
USS Arkansas (Old battleship)Capt. F. G. Richards, USN
FS Georges Levgues (Flag) (9-6", 8-3.5")Capt. de Vaisseau A. Laurin, FN
FS Montcalm (cruiser)Capt. E. J. H. L. Deprez, FN
HMS Glasgow (cruiser) 8-3.5"Capt. C. P. Clarke, RN
Of these, the two battleships were very old and their 12" guns were short range (20,000 yards) but very effective at medium to close ranges. The two French cruisers were not heavily gunned, nine 6" and eight 4" guns.
All in all these two groups were effective forces for the general purposes of bombardment. But not more than half the heavy ships could inflict serious damage upon the sort of protected batteries opposing them. If you must break a large rock with a small hammer, you must hit it a good many times. You must also see what you are doing so you keep hitting it in the right place. That, in our case, meant plenty of ammunition and expert spotting.
ref : https://www.history.navy.mil/content/history/nhhc/research/library/online-reading-room/title-list-alphabetically/n/naval-guns-normandy.html