These are the characteristics of the 28cm gun which I recently posted on a rel;ated thread in this forum:
Range
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Elevation With 727.5 lbs. (330 kg) APC L4,4 Striking Velocity Angle of Fall
2.0 degrees 5,470 yards (5,000 m) 2,513 fps (766 mps) 2.5
4.3 degrees 10,940 yards (10,000 m) 2,139 fps (652 mps) 5.7
7.4 degrees 16,400 yards (15,000 m) 1,824 fps (556 mps) 10.3
11.3 degrees 21,870 yards (20,000 m) 1,578 fps (481 mps) 17.2
16.2 degrees 27,340 yards (25,000 m) 1,430 fps (436 mps) 25.7
22.0 degrees 32,810 yards (30,000 m) 1,371 fps (418 mps) 35.3
29.2 degrees 38,280 yards (35,000 m) 1,404 fps (428 mps) 44.0
38.2 degrees 43,740 yards (40,000 m) 1,509 fps (460 mps) 52.0
Armor Penetration with 727.5 lbs. (330 kg) APC L4,4 Shell
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Range Side Armor Deck Armor
0 yards (0 m) 23.79" (604 mm) ---
8,640 yards (7,900 m) 18.09" (460 mm) 0.76" (19 mm)
16,514 yards (15,100 m) 13.18" (335 mm) 1.63" (41 mm)
20,013 yards (18,288 m) 11.47" (291 mm) 1.87" (48 mm)
30,000 yards (27,432 m) 8.08" (205 mm) 2.99" (76 mm)
Note: The above information is from "Battleships: Axis and Neutral Battleships in World War Two" for a muzzle velocity of 2,920 fps (890 mps) and is based upon the USN Empirical Formula for Armor Penetration.
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Range Side Armor Deck Armor
10,936 yards (10,000 m) 13.70" (348 mm) ---
16,404 yards (15,000 m) 11.02" (280 mm) ---
21,872 yards (20,000 m) 8.86" (225 mm) ---
27,340 yards (25,000 m) 7.64" (194 mm) ---
Note: The above information is from "German Capital Ships of World War Two." The data is based upon the pre-war Krupp test shoots on their range in Meppen with L/4,4 APC projectiles using RPC/32 propellant against KC-type armor at an impact angle of 70 degrees.
I copied all of this data from the site
German 28 cm/54.5 (11") SK C/34
The Iowas had the following armouring scheme
Main Belt 12.1 case hardened steel on ).875 STS (Special Tensile Steel)
Deck: 6 in and 1.5 weather deck, on 0.625 STS
Bulkheads: 11.3 in
The Nav weapons data shows that the Iowas deck protection scheme was more or less completely immune to damage at any practical eange. To penetrate the side armour, the 28cm round would need to close to somewhere between 12-15000 metres to ahave any hope of a main belt penetration. For a Battleship, this is extremely close range, essentially point blank range in fact.
In comparison the USN 16/50 Mk VII has the following characteristics:
Range
.
Elevation With 2,700 lbs. (1,224.7 kg) AP Mark 8 (new gun) With 1,900 lbs. (861.8 kg) HC Mark 13 (new gun)
10 degrees 17,650 yards (16,139 m) 18,200 yards (16,642 m)
15 degrees 23,900 yards (21,854 m) 24,100 yards (22,037 m)
20 degrees 29,000 yards (26,518 m) 28,800 yards (26,335 m)
25 degrees 33,300 yards (30,450 m) 32,700 yards (29,901 m)
30 degrees 36,700 yards (33,558 m) 36,000 yards (32,918 m)
35 degrees 39,500 yards (36,119 m) 38,650 yards (35,342 m)
40 degrees 41,430 yards (37,884 m) 40,600 yards (37,163 m)
45 degrees 42,345 yards (38,720 m) 41,622 yards (38,059 m)
Notes:
1) With reduced charges, the AP Mark 8 had a maximum range of 24,180 yards (22,110 m) while the HC Mark 13 had a maximum range of 27,350 yards (25,010 m).
2) Time of flight for AP Shell with MV = 2,500 fps (762 mps)
10,000 yards (9,140 m): 13.2 seconds
20,000 yards (18,290 m): 29.6 seconds
30,000 yards (27,430 m): 50.3 seconds
36,000 yards (32,920 m): 66.1 seconds
40,000 yards (36,580 m): 80.0 seconds
3) Time of flight for HC Shell with MV = 2,615 fps (797 mps)
10,000 yards (9,140 m): 13.1 seconds
20,000 yards (18,290 m): 30.3 seconds
30,000 yards (27,430 m): 53.2 seconds
35,000 yards (32,000 m): 70.3 seconds
39,500 yards (36,120 m): 86.0 seconds
4) The maximum range with the originally planned 2,240 lbs. (1,016 kg) AP Mark 5 was 47,000 yards (42,980 m). Muzzle velocity would have been 2,700 fps (823 mps) with a charge of 640 lbs. (290 kg) SPD.
5) At an "average gun" MV of 2,425 fps (1,739 mps), the maximum range with AP Mark 8 at a 40 degree elevation was 40,185 yards (36,745 m
Armor Penetration with 2,700 lbs. (1,224.5 kg) AP Mark 8
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Range Side Armor Deck Armor Striking Velocity Angle of Fall
0 yards (0 m) 32.62" (829 mm) --- 2,500 fps (762 mps) 0
5,000 yards (4,572 m) 29.39" (747 mm) 0.67" (17 mm) 2,280 fps (695 mps) 2.5
10,000 yards (9,144 m) 26.16" (664 mm) 1.71" (43 mm) 2,074 fps (632 mps) 5.7
15,000 yards (13,716 m) 23.04" (585 mm) 2.79" (71 mm) 1,893 fps (577 mps) 9.8
20,000 yards (18,288 m) 20.04" (509 mm) 3.90" (99 mm) 1,740 fps (530 mps) 14.9
25,000 yards (22,860 m) 17.36" (441 mm) 5.17" (131 mm) 1,632 fps (497 mps) 21.1
30,000 yards (27,432 m) 14.97" (380 mm) 6.65" (169 mm) 1,567 fps (478 mps) 28.25
35,000 yards (32,004 m) 12.97" (329 mm) 8.48" (215 mm) 1,555 fps (474 mps) 36.0
40,000 yards (36,576 m) 11.02" (280 mm) 11.26" (286 mm) 1,607 fps (490 mps) 45.47
42,345 yards (38,720 m) 9.51" (241 mm) 14.05" (357 mm) 1,686 fps (514 mps) 53.25
Note: The above information is from "Battleships: United States Battleships 1935-1992" for a muzzle velocity of 2,500 fps (762 mps) and is based upon the USN Empirical Formula for Armor Penetration. These values are in substantial agreement with armor penetration curves published in 1942.
This means that the Mk VII guns could start to engage the Scharnhorst from a massive 35000. Scharnhorst would need to close over 20000 yards relative range before she could effectively return fire. If the closure rate is say 2 knots (4000 yds per hour), it would take 5 hours of continous closure before the Scharnhorst could effectively return fire. Essentially, impossible I am afraid