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Old 06-04-2016, 01:05 PM   #111
Polydamas
 
Join Date: Jan 2006
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Default Re: [Basic] Skill of the week: Artillery (and Forward Observer)

Thanks for continuing to provide your real-life expertise! I think that one of the authors of GURPS 3e Guns (title on the cover: High Tech) and some later tech books was an American artilleryman in Vietnam, so I wonder how much of this is American experience in one period, as distorted by several rewritings and editorial interventions, versus Canadian in another.
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Old 06-04-2016, 01:25 PM   #112
roguebfl
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Default Re: [Basic] Skill of the week: Artillery (and Forward Observer)

Quote:
Originally Posted by johndallman View Post
This notation - ₥ - is unfamiliar. I'm guessing it means "mils", probably NATO mils (6400 to a complete circle), but an explanation would help.
https://en.wiktionary.org/wiki/%E2%82%A5 list it as milli- as is 1/10 of centi- (¢)
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Old 06-04-2016, 02:17 PM   #113
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Default Re: [Basic] Skill of the week: Artillery (and Forward Observer)

Sorry about the unexplained symbol. ₥ is short for mils (which is itself short for milli-radians). There are 2π radians in a circle and, in the military, it's rounded off to 6400₥, (except the Soviets apparently rounded it off to 6300). The old story is "There are 6282₥ in a circle. The Soviets said, 'That's stupid, we'll round it off to 6300₥.' and we said, "The Soviets are stupid. There are four cardinal directions, we'll round it off to 6400₥, so it works out even.'."

Last edited by Curmudgeon; 06-04-2016 at 02:23 PM.
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Old 06-04-2016, 02:59 PM   #114
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Default Re: [Basic] Skill of the week: Artillery (and Forward Observer)

Quote:
Originally Posted by Curmudgeon View Post
Sorry about the unexplained symbol. ₥ is short for mils (which is itself short for milli-radians). There are 2π radians in a circle and, in the military, it's rounded off to 6400₥, (except the Soviets apparently rounded it off to 6300). The old story is "There are 6282₥ in a circle. The Soviets said, 'That's stupid, we'll round it off to 6300₥.' and we said, "The Soviets are stupid. There are four cardinal directions, we'll round it off to 6400₥, so it works out even.'."
That story is very wrong, though; the Russian angular measurement was in 6000ths of a circle, based on an expansion from early Russian mathematicians who divided the circle into equilateral triangles (of which there are six to a circle) and then divided those into tenths, hundreds, and finally thousands. It was Sweden that rounded the circle to 6300 "streck".
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Old 06-06-2016, 04:55 AM   #115
Tomsdad
 
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Default Re: [Basic] Skill of the week: Artillery (and Forward Observer)

Curmudgeon, just want to say cheers for taking the time and effort here

Cheers

TD
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Old 12-30-2017, 03:17 PM   #116
jes722
 
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Default Re: [Basic] Skill of the week: Artillery (and Forward Observer)

We used it when we used W40K for bigger battles! I had FW skill and used to get more precise hits with indirect weapons!
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Old 01-24-2018, 01:12 PM   #117
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Default Re: [Basic] Skill of the week: Artillery (and Forward Observer)

Some part of my brain that was still thinking abut this came up with a house-rule that looks playable, and preserves some 4e RAW:

Gunner, DX/E, is the skill of operating weapons larger than small arms. Attack rolls made with it are DX-based, and either direct fire, or indirect fire observed from the weapon position. It has the existing Gunner specialisations, plus Catapult, Guided Missile and Torpedo.

Artillery, IQ/A, is the skill of calculating weapon paths and trajectories, used for calculating indirect fire, torpedo courses, and the like. Attack rolls made with it are IQ-based, except in unusual circumstances. The ST-based Artillery roll is transferred to Gunner. It has specialisations of Beams, Bombs, Guns, Catapults, Guided Missiles and Torpedoes.

Forward Observer is an optional specialisation of Artillery, and the specialisations of Artillery are familiarities for it.
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Old 03-26-2018, 01:06 PM   #118
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Default Re: [Basic] Skill of the week: Artillery (and Forward Observer)

I was asked about railway guns, and the Paris Gun in particular, some time ago. I think by whswhs. They aren’t really my field of expertise, but it seems there were good reasons for abandoning the concept. Here’s what I was able to find out.

208 mm (8”) calibre, or thereabouts, had been the upper practical limit for land-based mobile artillery prior to the Russo-Japanese War and that is still the case today. Larger calibre artillery pieces exist but they have been fixed emplacements, such as coastal defence artillery or, if mobile, naval artillery.

Up until the Battle of the Yellow Sea (10 August, 1904), large calibre (e.g., 320 mm or 12”) naval artillery had been obliged to hold their fire until they had closed to within three or four miles rather than their theoretical range of eight miles, as gun sights and rangefinders with the necessary accuracy were unavailable.

During the siege of Port Arthur (February through December, 1904) the Japanese dismounted some of their 280 mm (11”) howitzers from their coastal defence emplacements and used them to assist in breaking the fortifications at Port Arthur.

Railway guns begin with the German 420 mm/L12 (16.5”) short naval cannon “Dicke Bertha” (usually translated as Big Bertha, though it seems Dicke is actually closer to Heavy, Hefty or Fat Bertha), the Austrian 380 mm/L17 (15”) siege howitzers “Barbara” and “Gudrun”, and the Austrian 305 mm/L10 (12”) siege mortar “Schlanke Emma” (“Skinny Emma"). These were all reactions to the novelty of using large calibre naval guns to reduce land fortifications, as attempted by the Japanese.

Production records were destroyed near the end of WWI, so production numbers are imprecise as sources vary. 12 “Big Berthas” were produced along with 18 to 20 additional barrels; some Big Berthas were up-gunned to a L30 barrel later in the war. In addition to “Barbara” and “Gudrun”, the Austrians ordered another 14 siege howitzers and 2 additional barrels. Only eight of the fourteen were issued before the end of the war; it’s not clear whether the additional barrels were issued or not. Somewhere between 72 and 79 “Skinny Emmas” were issued in three models, the M11 (original 26 ton), M11/16 (25 ton) and M16 (23 ton version).

The three types of pieces, “Big Bertha”, “Barbara” and “Skinny Emma” were primarily used to reduce fortifications. While the Austrians had continuing success with their weapons as they continued to encounter older style fortifications, the fortifications that the Germans encountered after Verdun were of newer construction which reduced the effectiveness of “Big Bertha.”

These larger weapons required large crews to man them, typically in the 70-78 man range, though the smaller “Skinny Emma” only required a crew of fourteen or fifteen. As well, they took considerable time to set up. For example, “Barbara” was transported in four parts, required twenty hours to excavate a pit for its bedding, with a further eight hours to put the gun together in the pit. Additionally, “Barbara’s” 750 kg (3/4 ton) shell was loaded using a hand-powered winch!

The 380mm/L45 (15”) “Langer Max” (“Long Max”) is the stereotypical railway gun. They were originally intended as armament for the Bayern-class battleships but were deployed for land service when those ships were delayed. Initially they were deployed in fixed positions that used concrete requiring at least a month to construct. Near the end of 1917, a combination railway mounting/firing platform was developed which allowed quicker emplacement and greater mobility. Like most naval guns, the “Long Max” had very little off-bore capacity of its own (2° total traverse). With the railway mounting/firing platform, the “Long Max” could be traversed 360°. This did require installing a circular railway track to traverse on. Like the “Big Berthas”, the “Long Maxs” were navy weapons and crewed with navy personnel. (This may have been a simple case of needing someone to crew it, having the naval personnel already trained to use it and at loose ends as the ships they should have been assigned to were unavailable.) There appear to have been eight “Long Maxs”: seven were retained by the navy (and it appears they all became the Paris gun); one was transferred to the army (Saxon Battery).

The Paris Gun

Initially, the Paris Gun used worn-out “Long Max” barrels with a liner choking the interior diameter down to 210 mm (8”) from 380 mm (15”), later enlarging it to 240 mm (9”). With the smaller bore, the shell weight dropped from 750 kg to 106 kg (and then raised to 120 kg). The gun was initially required to have a 60-mile range, requiring the barrel to almost double in length. This requirement was met by shrinking the “Long Max” barrel onto a 98-foot rifled tube (usually referred to as the barrel liner). Once it was built the requirement was changed to a 75-mile range. To reach the new range the barrel needed to be an additional twenty feet longer. This presented two problems. There was no boring mill anywhere in Germany that could handle boring the extra length; and no one had ever successfully joined two rifled tubes together while keeping them aligned. In the end, it was decided that the initial 98-foot length would get the projectile spinning fast enough, so a smooth-bore tube would be good enough for the barrel extension.

The lengthened barrel, reduced projectile weight and presumably keeping the same amount of propellant increased the effective firing range from 22.2 km (14 miles) to 130 km (81 miles). The gun was always laid on the center (or zero) point of Paris. Small variations in firing conditions caused dispersion among the rounds. While twelve of the twenty-one rounds fired the first day fell within a two mile circle, two of the rounds had an eight mile separation, not only falling outside the city walls but landing at opposite ends of the city!

Between its first round on 21 Mar., 1918 and its last round, sometime around 8 August, 1918, the Paris gun fired somewhere between 320 and 370 shells. Seven barrels were made and none survived the end of the war. Barrels and liners wore out quickly. Each round fired eroded enough metal that the rounds were sequentially numbered, using a progressively thicker set of driving bands to seal the barrel. The chamber had to be re-measured for each firing, as it would advance by about 70 mm (not quite 3”), requiring additional propellant (approx. 10 kg) as compensation to maintain the range. (The propellant weight for the initial round in the 120 kg shell sequence was 180 kg.) A barrel with liner could fire only 65 rounds before being too worn for use. With an estimated average of 20 rounds fired per day, the barrel needed to be replaced every three days, i.e., a bit oftener than twice a week.

At first, it was thought that Paris was being bombed by a bomber or Zeppelin too high to be seen or heard, rather than shelled. However, before the day ended, sufficient shell fragments had been discovered to make it clear that the Parisians were being shelled. Credit for discovering the location of the Paris Gun within days is usually credited to French aviator, Didier Daurat.

However according to Col. H.W. Miller of the A.E.F., author of the book, The Paris Gun, which was based on formerly confidential information from both the Germans and French after the war, within an hour and a half of the first round, Entente officers had determined that the zero point of Paris was being targeted and shortly after the seventh round, they had a rough location of the Paris Gun, which was refined by sound ranging (measuring the differences in time of the echo of its firing at multiple locations simultaneously and then backtracking) within two to three hours of the first round.

The location was known accurately enough that the Entente dropped 5,000 rounds on the Paris gun and its four covering guns over the next five weeks, dropping over 100 rounds per hour near the end. One of the German guns burst, killing its crew, two positions were no longer able to be occupied, a third position was untenable when it was ordered to be abandoned and the fifth gun had worn out its barrel after just 64 rounds. Between them the five German guns had fired only 183 shells during the five weeks. That was according to German sources.

Last edited by Curmudgeon; 03-26-2018 at 02:18 PM. Reason: duplicated sentence
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Old 03-26-2018, 01:55 PM   #119
johndallman
 
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Default Re: [Basic] Skill of the week: Artillery (and Forward Observer)

Quote:
Originally Posted by Curmudgeon View Post
Here’s what I was able to find out.
Thanks very much for this.
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