In mid-1944, the Red Army recognized that it might need tanks that could consistently and reliably destroy the Wehrmacht’s most well-armored tanks. The Red Army fielded few tanks that could destroy the King Tiger, Elefant, and Jagdtiger reliably from medium-long ranges. Although it is true that the ISU-122, ISU-122s, ISU-152, and IS-2 were capable of destroying German heavy tanks, their combat results were not consistent enough. As a result, starting in June of 1944, five “BM” (“High Power” – Russian: “высокой мощности”) guns were developed for the ISU chassis. The resulting vehicles were: Object 243 (ISU-122-1 with the 122mm BL-9 gun), Object 246 (ISU-152-1 with the 152mm BL-8 gun), Object 247 (ISU-152-2 with the 152mm BL-10 gun), Object 250 (ISU-130 with the 130mm S-26 gun), and Object 251 (ISU-122-3 with the 122mm S-26-1 gun). More gun projects were being developed at this time, but no others appeared to be mounted onto a chassis. The guns proved capable, on paper, of destroying tanks such as the Jagdtiger, but testing showed that they were simply not practical. Moreover, these projects took well over a year to refine, and seeing as though the war ended before they were complete, they were all dropped.

自1944年以来，苏联红军意识到，他们需要一种能够可靠性良好的坦克，他能够轻松击毁德军使用的重装坦克。然而红军在战场上很少有能够在中远距离可靠的击穿虎王，象式，甚至猎虎的坦克。这是因为尽管他们拥有ISU-122，ISU-122s, ISU-152, 以及IS-2可以击穿德国的重型坦克的正面，但实际上战斗击穿率却不够稳定。因此，从1944年6月开始，俄军为ISU底盘开发了5门“BM”(俄语中“强力”的意思“высокой мощности”)主炮。而装载了这些火炮的底盘分别称为243工程(装载122mm BL-9火炮的ISU-122-1)，246工程(装载152mm BL-8火炮的ISU-152-1)，247工程(装载152mm BL-10火炮的ISU-152-2)，250工程(装载130mm S-26火炮的ISU-130)，以及251工程(装载122mm S-26-1 火炮的ISU-122-3)。其实还有更多的火炮项目在同步开发当中，但是真正装载在车体上的只有这五个。虽然理论上来说这些火炮都能够稳定击穿像猎虎这样的重型坦克，但是实验证明，这些坦克实际上是不可行的。另外，由于改进这些项目所花费的时间都超过了一年，因此直到战争结束都未能结束研制，因此它们也全部下马了。

Context: Soviet guns against German armor

苏联火炮 VS 德国装甲

为什么要发展这个项目?

Mythbusting: The SU-152 and ISU-152 were “Beast Killers”

流言终结者之一：SU-152和ISU-152是“动物园杀手”

Soviet wartime propaganda suggested that the SU-152 and ISU-152 (SU being based on the KV chassis, ISU being based on the IS chassis) were “Beast-Killers” because they could destroy Panthers, Tigers, and Elefants. The ISU-152’s 152mm ML-20S howitzer was, indeed, capable of destroying heavy German armor, but this required a direct hit with an High Explosive (HE) shell. Such a direct hit could do one of three things to disable the tank: destroy the vehicle’s drive systems, kill its crew, or blow the turret / casemate / hull open (or even clean off, in the case of turrets). Armor Piercing (AP) and Concrete Piercing shells were developed, but these were expensive and complicated to make, hardly more effective than HE rounds, and thus were scarcely supplied – even at Kursk! However, the ISU-152 was not a dedicated tank destroyer – it was an assault gun designed for bunker busting and indirect fire. Needless to say, using an assault gun as a tank destroyer was risky business.

苏联在战时的宣传材料中说SU-152和ISU-152(SU是KV的底盘，ISU是IS的底盘)是“动物园杀手”，因为它们可以干掉黑豹，虎式以及象式坦克。ISU-152的152mm ML-20S，说实话，的确可以一发摧毁德国的厚重装甲，然而，着必须要HE弹直接命中才行。这样的直接命中可以以三种方式的其中至少一种摧毁敌方：干掉敌方的行驶系统，击杀对方的成员，或者直接把炮塔/战斗室/车体击毁(甚至直接能把炮塔轰飞)。穿甲弹和混凝土穿彻弹虽然有，但是他们非常的昂贵，难以制造，而且不如HE炮弹性价比高，因此供给数量也不多——甚至在库尔斯克会战中也是如此!但是要考虑到ISU-152并非专业的坦克歼击车-它只是一门用来对付碉堡以及战场间接支援射击的突击炮而已。不用说，用突击炮来干坦歼的事并不是很明智的选择。

Firstly, the gun would need to be fired at short ranges against enemy tanks. This is because the ML-20S was a fairly low-velocity howitzer, which would simply not be accurate enough to engage tanks from distances. Consider also that the vehicle had a maximum of 90 mm of armor, which meant that it whilst it was adequately protected from some German guns at long ranges, it simply was not thick enough to protect the vehicle in the short ranges it would need to operate in as a tank destroyer. For example, the 7.5 cm KwK 40 L/48, as mounted on StuGs, Panzer IVs, and Jagdpanzers, could penetrate 97 mm of armor at 500 m, and 87 mm of armor at 1000 m, at 30 degrees (the ISU-152 casemate was barely sloped at all). Also consider that the vehicle was simply not mobile enough to be engaging more nimble German tanks, and could probably be outmaneuvered anyway.

首先，火炮需要抵近至非常近的距离以对抗敌方的坦克。这是因为ML-20S这门主炮是门有较低初速的榴弹炮，因此精度无法达到能够远距离击穿德国坦克的程度。虽然这辆火炮有着90mm的前装甲，可以在远距离防御住某些德国主炮的射击，但是近距离却无法像一辆一般的坦克歼击车一样防御住敌方的火力。举个例子，装载在IV号突击炮或者坦克歼击车上的7.5 cm KwK 40 L/48，可以在500m的距离上击穿97mm/30°的装甲，1000m为87mm/30°(而ISU的战斗室却几乎没有任何角度)。同时你还要考虑到这辆车的机动性也不是那么好，不足以对抗德国人的灵活的坦克，甚至有被绕菊花的可能性。

Yet another major issue of using the ISU-152 as a tank destroyer was that it could only manage 1-3 rounds per minute (depending if it had one or two loaders, and how experienced they were). This meant that in any type of ‘duel’, the ISU-152 would not only need to fire first, but also guarantee a hit, or practically any opposing German tank could get numerous shots off against it – as mentioned early, likely knock-out blows. Having said this, it did not seem to be a consideration taken into account when making the “BM” projects, as the guns all had equally as poor rates of fire.

ISU-152作为坦歼的另外一大缺点就是它的射速只能达到1-3发每分钟(具体取决于车内有一个还是两个装填手，以及他们是否有经验)。这也意味着当遭遇战打响时，ISU-152必须首先开火，并且保证命中，并且一发摧毁，要不然的话对方的德国坦克就能打回来数发炮弹将之摧毁。然而话是这么说，但是BM计划中似乎并没有考虑到相关的部分，因为这些炮没一个射速快的。

In conclusion, the ISU-152 did not live up to its legendary name. Other Soviet field guns and tank destroyers had somewhat better results compared to the ISU-152, although the results were still not quite satisfactory.

总之，ISU-152并没有传说中那么厉害(基佬十：啊♂幻想乡!)。其他的入役的火炮或者坦歼从某些程度来讲比ISU-152的战果都要强一些，尽管交换比也许不是那么漂亮

Mythbusting: The 122 mm A-19S and D-25T / S were sufficient

流言终结者之二：122mm A-19S和D-25T/S就足够了

It is a commonly held belief that the 122 mm D-25T / S and A-19S were sufficient at destroying the heaviest German armor. This belief is somewhat problematic, given the weight of the evidence.

很多人都觉得，122mm A-19S和D-25T/S就足以击毁最强大的德国装甲战车了。而根据不少的证据，这个想法多少也是错误的。

According to a Wa Preuf 1 (a Wehrmacht weapons research facility) report from October 5th, 1944, the 122mm A-19 (the A-19S being used on the ISU-122, the latest Soviet SPG at that time) could not penetrate the upper glacis of a Panther. However, it could penetrate the lower glacis from a distance of up to 100 m, the mantlet from 500 m, and the side of the turret from 1500m. This was still somewhat wanting, as the Red Army would prefer to engage such tanks from longer ranges, to prevent heavy losses of their own tanks.

根据一份来自Wa Preuf 1(某德国国防军武器研制所)，发表日期为1944年10月5日的报告说，122mm A-19(A-19曾经装在ISU-122上，是当时苏联最新的自行火炮)不能击穿黑豹的首上.但是，它可以在100m距离击穿首下，在500m击穿炮塔，并且在1500m击穿炮塔侧面。这也解释了为何红军会想要一款可以远距离击穿德国坦克的火炮，因为这可亿使己方坦克减少大量损失的几率。

The improved 122mm D-25T (which was used on the IS-2, the D-25S was essentially the same, and was used on the ISU-122S) seems to have fared much better against German armor. Testing of the gun on the IS-2 platform in Kubinka in 1944 suggests that a King Tiger’s turret (likely the side) could be penetrated from up to 1000-1500m. The welds of front hull seams could also be penetrated from 500-600m. Whilst these penetration statistics might make the D-25T sound more promising, they must be taken with some caveats.

而A-19的改进型122mm D-25T(装载于IS-2上，而D-25S与其基本类似，用于ISU-122S上)对抗德国装甲部队效果看起来要好很多。在1944年库宾卡进行的在IS-2平台上的D-25T可以在1000-1500m的距离击穿虎王的炮塔(估计是侧面)。即使是车体也可以在500-600m的距离上击穿。虽然这些数据听起来让人觉得D-25T已经够用了，但这还是不够。

Firstly, to score such hits would require a very skilled and very experienced gunner – especially to score a hit on the turret from a range of up to 1500m. Secondly, similar to the ML-20S, the D-25T could only manage up to 3 rounds per minute. Thirdly, the validity of these statistics has been called into question, because they come from Soviet sources. In the past, these statistics were often exaggerated for propaganda purposes. Finally, the very fact that the ISU “BM” projects were put into production suggests that the Soviets knew that the D-25T would not give consistently reliable results in AT duties.

首先，打出这样的数据肯定需要身经百战的炮手-特别是在1500m外射中炮塔这点。其次，就像ML-20S一样，D-25T的射速也就只有3发/分。第三，这些数据的真实性也有待考证，因为这只是苏联方面的一家之词。毕竟在二战哪个年代这些东西往往只是用作宣传。最后我们本文的主要话题，也就是BM计划的诞生，也恰恰证明了苏联自身是知道D-25T在反坦克能力方面并不理想的。

Whilst, indeed, the D-25T was, in theory, capable of destroying the heaviest German armor, it was perhaps not as reliable as it needed to be in the field. Of course, it is true that penetrations were not required to disable the tank or kill the crew (both in the case of the ML-20S and D-25T), but one could not simply rely on non-penetrating hits too, in some manner, disable the tank.

确实，D-25T从理论上来说肯定是能够击毁最强大的德军坦克的，只是在实战中并没有那么靠谱而已。当然，穿深对于击毁坦克或者击杀成员来说也许并不是那么重要(对于ML-20S或者D-25T来说)，但是，不可否认，如果不能击穿敌方坦克，也就无法保证能够使其失去战斗力。

As a result of these relatively unsatisfactory Soviet AT capabilities against the Wehrmacht’s heaviest tanks, in June 1944, Zavod Nr. 100 began developing new, high velocity 122 mm, 130 mm, and 152 mm guns to be mounted on the ISU (and perhaps IS and KV) chassis.

因为苏联难以对抗德军的重型坦克，1944年6月，100号工厂开始开发新的，高初速的，可以装在ISU底盘上(说不定也能在IS或者KV底盘上)的122mm，130mm，以及152mm主炮。

Object 243 (ISU-122-1)

243工程(ISU-122-1)

Object 243 (ISU-122-1) with the 122 mm BL-9. This vehicle is distinguishable as its gun has no muzzle brake, and looks like an elongated A-19S. However, the gun replicator has been angled (see the rectangular plate on the mantlet below the gun), unlike a regular ISU-122.

装有122mm BL-9的243工程。这车很容易就能被认出来，因为它的主炮没有制退器，而且看起来就像一门A-19S。然而，这门炮的复进器是带有角度的(可以看到主炮下方炮盾上的长方形装甲板)，这点和ISU-122不同。

can be distinguished by its gun and mantlet. The gun essentially looked like a longer version of the A-19S. The mantlet also had some tweaking to fit the longer and heavier gun – most notably, the tip of the gun replicator has been angled to one side (just below the gun).

243工程装配有122mm BL-9火炮-是BL家族火炮中非常著名的一员，由172设计局设计。这辆战车的特征在于其主炮和炮盾。主炮类似于A-19S的加长版本。炮盾也有某些改动，使其能够装备更长更重的主炮-最重要的一点是这门炮的复进器是向下倾斜的。

It could penetrate 204 mm of armor at 1000 m, with 2 rounds per minute.

1000m穿深为204mm，射速为2发/分钟

The gun’s muzzle velocity was 950 m/s with an 11.9kg AP shell.

炮口初速为950m/秒，炮弹重11.9kg

It had a range of 10,700 m, compared to the 6000 m range of the 152 mm ML-20S of theISU-152 and SU-152.

射程达10700m，而ISU-152和SU-152装备的152mm ML-20S的射程为6000m

It could carry 20 AP rounds, the same as the ISU-152.

备弹20发，和ISU-152相同

Like the other “BM” guns, the BL-9 was likely too powerful for its mountings, which caused mechanical issues.

和其他BM的主炮一样，BL-9的后坐力对于其载具来说太大，会造成一系列的机械问题。