kopyo-21 wrote:
Posts after posts, they become not only my logic and the reality but also the calculations that follows the Newton's momentum conservation. You write a lot, provide a lot of your assumption to avoid facing with both physics laws and reality:
kopyo-21 wrote:
1. Physics laws: According to the Newton's momentum conservation law, both 2 guns 2a42 and 2a72 fire same bullet (0.4 kg) with the same muzzle velocity (960 m/s) so right after the bullet leaving the barrel, both 2 guns must whistand the same momentum back (initial recoil).
Besides that, also right after the bullet leaving the barrel, the burning gas throut out from the gun muzzel makes gun like a rocket and the second recoil appears. Both 2 guns fire the same rounds (the same cartridge powder), have the same barrel length and groves design so their secondary recoil are the same.
You acknowledge the rocket effect of propellant gasses, and then you don't care about it. In your calculations, you used the momentum of the 0.4 kg projectile, and then ignored the propellant gasses entirely... You like to talk about "law of Newton" and "physics laws" when it suits you, and then you ignore them when they are inconvenient. You do this because you know that when you add the propellant gasses into the equation, the recoil force jumps from 6.2 kN to something much, much higher... and your illusion is shattered. So of course, you prefer to pretend that it does not exist
kopyo-21 wrote:
However, the 2A42 gun use the muzzle brake that helps to reduce the secondary recoil therefore its total recoil is lower than 2A72 at the moment the bullet leaving the barrel. (Don't make your owned assumption about the muzzle brake of 2A42 gun reduces 90% of recoil force)
I wrote so long like that to explain you and prove why I said both 2 guns produce the same recoil when firing but the muzzle brake makes the total recoil of 2A42 lower than 2A72
Also according to the Newton's momentum conservation law, right after receiving the recoil, both 2 gun's barrels move back to balance the force. It reduces the recoil by spreading it over the moving back so the longer moving back is, the lower force needed to stop is.
The 2A72 gun's barrel moves back 330 mm, much more (around 10 times) higher than the 30-35 mm of 2A42 gun's barrel so it spreads out the recoil much more effectively (around 10 times as calculation) than 2A42 gun. Therefore when the barrels stop (after 330 mm in 2A72 and after 30-35 mm in 2A42), the force that 2A72 gun's barrel push on the gun is much less than 2A42 gun's barrel do.
"To reduce the impact of the gun's release, the barrel is absorbed and recedes 30 to 35 mm when firing."
http://www.arms-expo.ru/armament/samples/1300/59779/
Just because the barrel moves back by 330-335mm does not mean that it decelerates at the same rate throughout. Here's what the technical description (Техническое описание и инструкция по эксплуатации 30-мм автоматической пушки 2А72.00.000.TO) for the 2A72 says:
При выстреле ствол вместе с затвором под действием пороховых газов на дно гильзы движется назад.
Ствол с затвором первоначально движется назад свободно сжимая возвратную пружину.
Пройдя=270мм начинают сжимать пружину аммортизатора. Сжав ее на 60-65мм энергия отката ствола поглощается, и они останавливаются.Translation:
When a shot is fired, the barrel, together with the bolt, moves backward under the action of the powder gases on the bottom of the cartridge case.
The barrel with the bolt initially moves backwards freely compressing the return spring.
Passing=270mm begins to compress the spring of the shock absorber. Compressing it by 60-65mm, the energy of the moving barrel is absorbed, and they stop.You tell me, what does it say about how far the barrel needs to stop? Keep in mind that the return spring is a tiny little spring whereas the shock absorber spring is a massive coil spring that wraps around the barrel, as you can see below (2. shock absorber, 6. return spring):
Deceleration is low when the return force is low, and deceleration is high when the return force is high. When the barrel is only compressing the tiny return spring, the barrel only loses a few meters/second in a long span of time, but when it compresses the huge shock absorber spring, it decelerates very quickly within a distance of 60-65mm. The small return spring is much smaller than the return spring for the 2A42, which has a much larger bolt carrier and bolt than the 2A72 so it needs a bigger return spring. Do you wonder why the technical description says "moves backwards freely"? It is because the barrel is barely slowing down at all before it contacts the shock absorber.
kopyo-21 wrote:
http://www.history147.ru/2017/09/blog-post.html?m=1
https://ru.m.wikipedia.org/wiki/30-мм_пушка_2А72
https://wikivisually.com/lang-ru/wiki/2А72
PS: I give all of suorces above not for the "7 tons" and the "20 tons" numberd as I can not determine where are come from. Just want to re-confirm that the 2A72, thank to its longer-recoil operation, has push much lower force on the turret and whole vehicles than the 2A42 do.
All these websites basically copy from ru.wikipedia, and the relevant paragraph from ru.ikipedia.ru has 0 sources. Literally 0. The page that you are quoting from was first edited by an
anonymous user on the 22rd of April 2017, who added the stuff about the 7mm roof: https://ru.wikipedia.org/w/index.php?title=30-%D0%BC%D0%BC_%D0%BF%D1%83%D1%88%D0%BA%D0%B0_2%D0%9072&direction=next&oldid=85004226
The second edit was made on June 29 and made a minor grammatical change, but it was otherwise identical. The third edit was done by another
anonymous user on the 5th of September 2017, who added the "7 tons vs 20 tons" statement without listing sources. If you compare this version of the wiki article with the previous versions, there were no changes in the references list: https://ru.wikipedia.org/w/index.php?title=30-%D0%BC%D0%BC_%D0%BF%D1%83%D1%88%D0%BA%D0%B0_2%D0%9072&direction=next&oldid=86258286
You were unable to find a source for "7 tons" and "20 tons" of recoil because those numbers were completely made up. 7 tons of recoil force is equal to 68 kN, and 20 tons is equal to 196 kN, which is absurd, of course. Just another case of article vandalism. It's pretty obvious that Wikivisually is just a website that automatically copies content from Wikipedia but with a photo gallery on the right side of the page, if you bothered to read the top right corner of the page you quoted, and the history147.ru blog article is also directly copied from Wikipedia. Compare them:
history147 blog:
Пушка 2А72 за счет применения схемы с подвижным стволом, по сравнению с газоотводной на 2А42 передает на крышу бронеобъекта более растянутый по времени импульс отдачи, а значит имеет меньшее максимальное значение силы отдачи, что позволяет использовать ее на легкой бронетехнике типа БТР-82, Тигр-М с бронекорпусами выполненными из листов толщиной всего около 7 мм, на которой применение вооружения мощнее 14,5мм пулемета КПВТ до появления 30мм пушки 2А72 ранее было невозможно. Это ставит, по огневым возможностям, их на один уровень более тяжелыми и дорогими БМП и значительно повышает боевую ценность легких бронемашин в обороне (когда бой ведется из окопа и уровень бронезащиты боевой машины не столь важен).Wikipedia edit from the 29th of June, 2017:
Пушка 2А72 за счет применения схемы с подвижным стволом, по сравнению с газоотводной на 2А42 передает на крышу бронеобъекта более растянутый по времени импульс отдачи, а значит имеет меньшее максимальное значение силы отдачи, что позволяет использовать ее на легкой бронетехнике типа БТР-82, Тигр-М с бронекорпусами выполненными из листов толщиной всего около 7 мм, на которой применение вооружения мощнее 14,5мм пулемета КПВТ до появления 30мм пушки 2А72 ранее было невозможно. Это ставит, по огневым возможностям, их на один уровень более тяжелыми и дорогими БМП и значительно повышает боевую ценность легких бронемашин в обороне (когда бой ведется из окопа и уровень бронезащиты боевой машины не столь важен).Would it be a surprise to you if I told you that the history147.ru article was written on the 3rd of September, 2017? Just two days before the Wikipedia article on the 2A72 was edited on the 5th of September and the "7 tons vs 20 tons" rubbish was added, and for that reason, the history147.ru article is only identical to the Wikipedia page on the 2A72 from June 29. So in summary:
- April 22: "7mm roof" appears on Wikipedia without references or sources of any kind
- June 29: Minor grammatical change
- September 3: history147.ru article copies June 29 version of Wikipedia article on 2A72
- September 5: "7 tons vs 20 tons" appears on Wikipedia without references or sources of any kind
The "7mm roof" claim was originally made on a Wikipedia article and has no sources, and the author of that claim was an anonymous person from Moscow, so nobody with a name is taking responsibility for it. No wonder, since it's such a stupid claim! The BMP-2 has a roof that is 6mm thick, and guess what cannon it has? This little detail allows us to conclusively confirm that all of the sources you listed are in fact direct copy-and-paste jobs taken from an unsourced Wikipedia article. Your sources get worse and worse. First it was weaponsystems.net, a website with articles written by anonymous authors and has no references or sources, and now it's Wikipedia, a website with an article written by an anonymous author that has no references or sources. This is what you're leaning on. These are your sources. This is what you're basing your entire argument on.
kopyo-21 wrote:
2. The reality: Sofar, all projects that upgrade or newly produce wheeled combat vehicles that have been bought by both domestic and oversea like BTR-80A, BTR-82A, BTR-3/4 in Russia and Ukraine have been using 2A72 instead of 2A42. In contrasts, no one has bought vehicles with 2A42 gun like BTR-90, BTR-82A1, etc.
Again you talk about this. Many products have been offered over the years, not all have entered service. It's natural. Often it's about manufacturing capabilities. Muromteplovoz makes turrets with a 2A42 that could have been used for the BTR-82A, but they also had the same turret except with a 2A72 instead of a 2A42, so they could have bought that instead. See photo:
Why not? Maybe Muromteplovoz does not have the kind of manufacturing capacity to produce thousands of turrets. After all, they have been mostly doing overhaul work for years. Speaking of the BTR-82A, you need to realize that even though the BTR-80A, BTR-82A, and BRM-3K all have a 2A72, the barrels on their guns are unsupported. What happens when the barrel is unsupported? According to a proposal document titled
Новые Технологии Создания Малокалиберных
Автоматических Пушек:
Например, в одной из работ была выбрана 30-мм пушка 2А72 широко применяемая в сухопутных войсках. Достоинством этой пушки является селективное питание и надежность. Пушка имеет низкий темп стрельбы, он составляет около 400 выстр./мин., что позволяет более экономно расходовать боекомплект. Недостатками является так называемый эффект «хлыста» – ствол при выстреле испытывает на себе мощные колебания, что приводит к резкому снижению точности при стрельбе очередью. Данный недостаток решается помещением стола в направляющие (БМД-4 и БМП-3) или сильным снижением темпа стрельбы (БТР-80А)Translation:
For example, in one of the works chosen was 30-mm gun 2A72 widely used in the army. The advantage of this gun is selective feed and reliability. Gun has a low rate of fire, about 400 RPM, which allows for more economical use of ammunition. The disadvantage is the so-called "whip" effect - when a shot is fired the barrel experiences powerful vibrations, which leads to a sharp reduction in accuracy when firing bursts. This disadvantage is solved by putting the barrel in guides (BMD-4 and BMP-3) or a strong decrease in rate of fire (BTR-80A).Yes, what Alexander Blagonravov said is absolutely correct. Low accuracy of the 2A72 was solved by putting a barrel support, but only on the BMP-3. If a 2A72 has no barrel support, it can only be fired with a "strong decrease in the rate of fire", meaning that the cost of mounting a 2A72 in a BTR-80A/82A or a BRM-3K (recon vehicle based on BMP-3 without 2A70) is a huge reduction in accuracy that is only avoided by firing slowly or by firing in single shots only. That's why the BTR-80A has three settings for the 2A72: semi-auto, 200 RPM, and 330 RPM. It says so in the technical manual (TO BTR-80A). Also, the early prototypes of early Pantsirs were equipped with dual 2A72s (unsupported barrels) instead of 2A38Ms, and the combined rate of fire from the two guns was 440 RPM, or 220 RPM each. Given this track record of ignoring the need for a barrel support on a cannon that clearly needs it, suggesting that the 2A42s on the BMPT should be replaced with 2A72s is just irresponsible.
Anyhow, I know you like to use the Tigr-M as an example of the "low recoil" of the 2A72, so let's ask the question of how were they able to stick a 2A72 onto the roof of a small 4x4 car: No, it's not because 2A72 has such low recoil that it can be installed on a roof that is "less than 7mm thick". It's because they had to build an intrusive structural support inside the cabin to support the turret, reducing the number of passenger seats in the cabin from 7 to just 2, as you can see in the photos below.
On the other hand, the installation of the 2A42 in an unmanned turret in the Typhoon-VDV had a much, much less effect on the inhabitable space inside the car.
kopyo-21 wrote:
PS 1: BTW, you should revise the data about firing accuracy of 2A42 in your blog. The given data is totally incorrect that may makes you and your readers percept wrongly not only about 2A42 bust also about 2A72.
PS 2: The 2A42 is nothing better than the 2A72 (with barrel's rigid sleeve support) but only ROF.
PS 3: In the contrasts, the 2A42 is bigger, more expensive, smockier and much more recoil than the 2A72.
PS 4: Sofar, you still can not prove anything that you use to fight back my points, suggest replacing the 2A42 by 2A72 on new generation of BMPT.
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Your proposal to mount two 2A72s to replace the two 2A42s and increase the firerate of the 2A72s "with some modifications" demonstrates a total lack of understanding of the mechanism of the 2A72. The long-recoil action limits its fire rate to around 330 RPM, and the cannon fires at its maximum RPM at all times. It cannot go any faster.
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At first, it was 40-50 kN gets reduced to 30-40 kN. Then 2A42 suddenly has the same recoil force as 2A72, so now it is 60 kN gets reduced to 30-40 kN. 
