II. Weapons Systems
Roma was equipped with six different weapons systems to engage sea, land, and air targets with maximum effectiveness.
1. Primary system is the main battery of nine 381mm (15 inch) 50 caliber rifles in three three-gun turrets. Two forward, one aft.
2. Secondary battery consists of 12 152.4mm (6 inch) 55 caliber rifles in four triple turrets. One mount in each corner of the superstructure.
3. Tertiary battery and primary anti-aircraft system is made up of 12 90mm 50 caliber guns in stabilized single-gun turrets.
4. Twenty 37mm 54 caliber AA guns in eight twin and four single mounts.
5. Twenty-eight 20mm 65 caliber AA guns in 14 twin mounts.
6. Four single 120mm 40 caliber rifles equipped with star shells for illumination purposes.
There were 24 rangefinder in various positions.
1) The 381/50 guns were very powerful weapons developed out of the requirement to match foreign 16in./406mm performance without the investment in a domestic 406mm design. By increasing charge power, shell flight characteristics, and lengthening the barrels, the Italian 381/50 possesses the second longest theoretically maximum range of a traditional large caliber naval rifle behind only the Japanese 460mm/18.1inch. This incredible range came at a price: barrel life was, at best, 140 rounds per liner due to the extreme pressures. For contrast, the long German 38cm on the Bismarck was rated at 240 rounds.
A total of forty guns were produced. Only the nine lost on the
Roma appear to have escaped the cutting torch.
Rate of fire tended to average around 1.3 rounds per minute. Around 45 seconds to reload and re-aim.
Much has been made of problems related to excessive dispersion or poor ammunition, however modern research does seem to point to a combination of factors preventing satisfactory performance at the time of induction. Time and resource constraints at the commencement of hostilities prevented the full work up of the weapons so necessary to good performance on all three ships. It was not until 1942 that the first two sisters began to shoot more effectively, at which point these ships were guarded very carefully. The first breakthrough in improving dispersion was to increase the delay between the outer barrels and the middle gun firing. Barrels simultaneously firing next to each other create tremendous pressures that can push adjoining shells apart ever so slightly. By imparted a multi-millisecond delay, the middle (or outer, depending on which is to fire first) shell can travel unimpeded. The second major improvement was a slight reduction in charge power resulting in a reduction in muzzle velocity from 890m/s to 870m/s (still considerable!), this move reduced dispersion, reduced horizontal armor penetration, increased trajectory, and increased vertical armor penetration proportionally. These changes combined with increased practice (like piano, practice makes perfect
) resulted in a very satisfactory gun. Indeed, the Italian 381mm system was not the worst offender in the dispersion struggle: both the French 15 inch and British 14 inch programs faced greater challenges on the road to 'perfection'. Of Italian weapons, the 381mm was more accurate and had less dispersion than the 'new' 320mm mounted on the four legacy battleships.
The standard shell (referred to in the
Regia Marina as 'ball') was an armor piercing shell of 885kg or 1951.09 pounds. Propellant charge was 264kg of NAC and FC4 (I have no idea what composition either of those are, please enlighten me if you know.). Range at maximum elevation is 42,800 meters (26.59 miles). Effective range was, of course, significantly lower. The high muzzle velocity's primary payoff was at close ranges where flat firing arcs against vertical armor would lead to penetration values similar to larger 16 inch rifles due to shallower angle of impact and reduced reliance on normalization.
There was also a lighter semi-armor piercing shell at 824kg.
Average fighting range was thought to be 18,500 meters. This corresponds to around 9 degrees of gun elevation. Shell travel time at this range is 26.35 seconds. At this rage, the 381mm shell could penetrate in excess of 416mm (the figure for 19,000 meters range) of steel at 90 degrees.
2) The 152/55 guns were mounted in the same triple turrets seen in the Abruzzi class of light cruiser. These were powerful weapons with long barrels, reflecting the Italian philosophy favoring high striking velocities. Rate of fire was acceptable but inferior to newer 6 inch designs like the US 6 inch/47. Reload times averaged 14 seconds.
Range was 25,700 meters with a shell weight of 49.6kg and a muzzle velocity of 925m/s.
3) The 90mm guns were revolutionary. Although not as much as was intended. These were the among the first fully stabilized dual purpose mounts installed on warships. Performance of the guns themselves was apparently spectacular, however the new and advanced oscillating motor system was complex with many points of failure. In combat, rate of fire was one round every five second. An interesting feature of the mounting was that it was welded to the deck without penetrating it thus preserving the integrity of the armored deck.
4) The 37mm guns were air cooled guns with and effective rate of fire of 140 rounds per minute because of hand loading. They had a six round loading tray. These mounts had a simple stabilization device to offset a limited amount of heel in the base of the mounting (not on the singles).
5) The 20mm had an effective rate of fire of 150 rpm. Barrels were mounted diagonally offset in twin mounts, a visually engaging approach.
6) The 120mm guns were reclaimed from older armored cruisers (which specific ships possessed
Roma's four originally I do not know. They exclusively to be used for illumination purposes. Nominally they could light targets up to 10km away but in practice it seems that 5km was the effect range. These guns were deemed to be ineffective in their task and slated for replacement. However the exigencies of war precluded solutions. The were installed on the
Roma anyway.
II. Weapons Systems
[i]Roma[/i] was equipped with six different weapons systems to engage sea, land, and air targets with maximum effectiveness.
1. Primary system is the main battery of nine 381mm (15 inch) 50 caliber rifles in three three-gun turrets. Two forward, one aft.
2. Secondary battery consists of 12 152.4mm (6 inch) 55 caliber rifles in four triple turrets. One mount in each corner of the superstructure.
3. Tertiary battery and primary anti-aircraft system is made up of 12 90mm 50 caliber guns in stabilized single-gun turrets.
4. Twenty 37mm 54 caliber AA guns in eight twin and four single mounts.
5. Twenty-eight 20mm 65 caliber AA guns in 14 twin mounts.
6. Four single 120mm 40 caliber rifles equipped with star shells for illumination purposes.
There were 24 rangefinder in various positions.
1) The 381/50 guns were very powerful weapons developed out of the requirement to match foreign 16in./406mm performance without the investment in a domestic 406mm design. By increasing charge power, shell flight characteristics, and lengthening the barrels, the Italian 381/50 possesses the second longest theoretically maximum range of a traditional large caliber naval rifle behind only the Japanese 460mm/18.1inch. This incredible range came at a price: barrel life was, at best, 140 rounds per liner due to the extreme pressures. For contrast, the long German 38cm on the Bismarck was rated at 240 rounds.
A total of forty guns were produced. Only the nine lost on the [i]Roma[/i] appear to have escaped the cutting torch.
Rate of fire tended to average around 1.3 rounds per minute. Around 45 seconds to reload and re-aim.
Much has been made of problems related to excessive dispersion or poor ammunition, however modern research does seem to point to a combination of factors preventing satisfactory performance at the time of induction. Time and resource constraints at the commencement of hostilities prevented the full work up of the weapons so necessary to good performance on all three ships. It was not until 1942 that the first two sisters began to shoot more effectively, at which point these ships were guarded very carefully. The first breakthrough in improving dispersion was to increase the delay between the outer barrels and the middle gun firing. Barrels simultaneously firing next to each other create tremendous pressures that can push adjoining shells apart ever so slightly. By imparted a multi-millisecond delay, the middle (or outer, depending on which is to fire first) shell can travel unimpeded. The second major improvement was a slight reduction in charge power resulting in a reduction in muzzle velocity from 890m/s to 870m/s (still considerable!), this move reduced dispersion, reduced horizontal armor penetration, increased trajectory, and increased vertical armor penetration proportionally. These changes combined with increased practice (like piano, practice makes perfect :big_grin: ) resulted in a very satisfactory gun. Indeed, the Italian 381mm system was not the worst offender in the dispersion struggle: both the French 15 inch and British 14 inch programs faced greater challenges on the road to 'perfection'. Of Italian weapons, the 381mm was more accurate and had less dispersion than the 'new' 320mm mounted on the four legacy battleships.
The standard shell (referred to in the [i]Regia Marina[/i] as 'ball') was an armor piercing shell of 885kg or 1951.09 pounds. Propellant charge was 264kg of NAC and FC4 (I have no idea what composition either of those are, please enlighten me if you know.). Range at maximum elevation is 42,800 meters (26.59 miles). Effective range was, of course, significantly lower. The high muzzle velocity's primary payoff was at close ranges where flat firing arcs against vertical armor would lead to penetration values similar to larger 16 inch rifles due to shallower angle of impact and reduced reliance on normalization.
There was also a lighter semi-armor piercing shell at 824kg.
Average fighting range was thought to be 18,500 meters. This corresponds to around 9 degrees of gun elevation. Shell travel time at this range is 26.35 seconds. At this rage, the 381mm shell could penetrate in excess of 416mm (the figure for 19,000 meters range) of steel at 90 degrees.
2) The 152/55 guns were mounted in the same triple turrets seen in the Abruzzi class of light cruiser. These were powerful weapons with long barrels, reflecting the Italian philosophy favoring high striking velocities. Rate of fire was acceptable but inferior to newer 6 inch designs like the US 6 inch/47. Reload times averaged 14 seconds.
Range was 25,700 meters with a shell weight of 49.6kg and a muzzle velocity of 925m/s.
3) The 90mm guns were revolutionary. Although not as much as was intended. These were the among the first fully stabilized dual purpose mounts installed on warships. Performance of the guns themselves was apparently spectacular, however the new and advanced oscillating motor system was complex with many points of failure. In combat, rate of fire was one round every five second. An interesting feature of the mounting was that it was welded to the deck without penetrating it thus preserving the integrity of the armored deck.
4) The 37mm guns were air cooled guns with and effective rate of fire of 140 rounds per minute because of hand loading. They had a six round loading tray. These mounts had a simple stabilization device to offset a limited amount of heel in the base of the mounting (not on the singles).
5) The 20mm had an effective rate of fire of 150 rpm. Barrels were mounted diagonally offset in twin mounts, a visually engaging approach.
6) The 120mm guns were reclaimed from older armored cruisers (which specific ships possessed [i]Roma's[/i] four originally I do not know. They exclusively to be used for illumination purposes. Nominally they could light targets up to 10km away but in practice it seems that 5km was the effect range. These guns were deemed to be ineffective in their task and slated for replacement. However the exigencies of war precluded solutions. The were installed on the [i]Roma[/i] anyway.
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