tag:blogger.com,1999:blog-5030145265861917845.post8688372418494592232..comments2024-03-28T14:35:30.147-04:00Comments on Tank Archives: Heavy Tank DestroyerPeterhttp://www.blogger.com/profile/09622237223229485503noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-5030145265861917845.post-64090443849628019032020-07-28T12:07:38.047-04:002020-07-28T12:07:38.047-04:00@Steward Millen, I would like to point out the A-1...@Steward Millen, I would like to point out the A-19 (800m/s) is more powerful than the D-25T (781m/s).<br /><br />@Peter, I don't understand why the first testers disliked the screw breach and wanted a sliding breach and the second testers demanded the screw breach?Mobiushttps://www.blogger.com/profile/05256982406940327658noreply@blogger.comtag:blogger.com,1999:blog-5030145265861917845.post-78967536707125350612020-07-28T12:02:47.380-04:002020-07-28T12:02:47.380-04:00This comment has been removed by the author.Mobiushttps://www.blogger.com/profile/05256982406940327658noreply@blogger.comtag:blogger.com,1999:blog-5030145265861917845.post-3907523538679220212020-07-28T07:56:20.173-04:002020-07-28T07:56:20.173-04:00Savings in structural and mechanical complexity as...Savings in structural and mechanical complexity aside, the whole point of yanking out the turret and converting the fighting compartement into a gun casemate tended to be specifically the ability to plunk in a bigger boomstick. No more worries about turret ring diameters etc.<br /><br />The general rule of thumb seems to have been that a casemate could take a gun *at least* one "grade" bigger than a turret on the same base chassis, or even bigger if a comparatively low-velocity howitzer was used. Eg. T-34 (76 mm) vs. SU-85 (85 mm) or SU-122 (122 mm how.), Panther (75 mm) vs. Jagdpanther (88 mm), KV-1 (76 mm) vs. SU-152 (152 mm how.)(KV-2 with its ludicrously oversized turret can be ignored here), Pz IV (75 mm) vs. Jagdpanzer IV (higher-velocity 75 mm) or Sturmpanzer (150 mm how.), T-70 (45 mm) vs. SU-76 (76 mm)...<br />You get the idea.<br /><br />The turret ring certainly creates something of a problem spot in overall recoil absorption but near as I've ever heard in practical terms this is largely irrelevant; it so limits the space available for the turret's internal "payload" space and physically manipulating the ammunition as to render it all but physically impossible to fit in a gun with recoil in excess of what a properly designed turret ring of a given diameter can structurally absorb.<br /><br />Case in point, IIRC the KV turret ring diameter was not markedly enlarged during the creation of the KV-2 whose humongous turret could operate a 152 mm gun-howitzer (literally twice the bore of the gun the chassis was originally designed to carry) just fine, and served as a testbed for the firing trials of the 107 mm gun project too. And wasn't a T-28 similarly fitted with a 85 mm gun as a trial platform too, with even fewer structural changes?<br /><br />Near as I'm aware as long as you could actually physically attach the turret and gun to the hull turreted AFVs normally had no structural trouble with the recoil of guns way past what they were originally designed for - if memory serves the Americans successfully enough trialed their new 90 mm gun on both the stalwart Sherman and the go-kart Hellcat. Biggest issue was usually excessive rocking of the hull from the recoil impulse and the added mass.<br /><br />The Army did have some prior history with (and old guns in) the 107 mm caliber going back to Imperial Russian times but those were never very numerous and got eventually dropped altogether; one somewhat gets the impression the landlubbers never quite found a real role for them or liked them all that much. Such niche as they now had was later taken up by the next-gen 100 mm jobs - ultimately derived from interwar Navy DP/AA designs, ironically, but then AA guns tended to be the universal go-to when armies shopped around for starting points for powerful direct-fire guns anyway.<br /><br />The 130 mm lineage was also an old Imperial Navy legacy but had virtually no prior presence whatsoever in the ground forces - about the only exception I know of is the SU-100Y SPG converted from the T-100 prototype (it was conceived as a bunker buster in the general scramble for such designs in the wake of the Winter War; now at Kubinka). The caliber kept getting floated as a proposed armament for AFVs at least as late as the Object 785 MBT project of the late Seventies but one rather gets the impression the Army never really warmed to it before the advent of smoothbores rendered the point moot.Kellomieshttps://www.blogger.com/profile/04915110653443066212noreply@blogger.comtag:blogger.com,1999:blog-5030145265861917845.post-88676987508196969312020-07-27T14:12:47.903-04:002020-07-27T14:12:47.903-04:00Kellomies, one would think that the omission of a ...Kellomies, one would think that the omission of a turret would if anything reduce the interior space, not increase it, though I lack the interior dimensions of say, the T34/85 vs the SU-100 to demonstrate yay or nay (it's hard for me to fathom how one can claim that an assault gun's lower profile does anything else). While it's true that it's not just the turret that absorbs the recoil, the turret/chassis linkage is undeniably a weak spot for absorbing gun recoil. And you get around that issue by mounting the weapon directly in the chassis and omitting the turret; or at least that's always been the explanation I've read.<br /><br />The 130 mm gun *was* being considered for the IS-7, so the opposition to it couldn't have been that intense. It's not like it was an entirely new caliber for the Soviet military. And we're talking about the postwar period, when some lag time setting up the logistics for the weapon could be acceptable. <br /><br />Personally, I think that such an "ISU-130" with improved armor protection and a 130 mm gun that still comes in under 50 tons makes a lot more sense than an IS-7. It would put that very powerful gun on any prospective battlefield in a fairly survivable chassis, and do it economically.Stewart Millenhttps://www.blogger.com/profile/01261690405884935161noreply@blogger.comtag:blogger.com,1999:blog-5030145265861917845.post-27834075858203696792020-07-26T19:55:24.556-04:002020-07-26T19:55:24.556-04:00Would point out the main reason, AFAIK, why turret...Would point out the main reason, AFAIK, why turretless SPGs can mount bigger guns than turreted tanks on basically the same hull/otherwise of similar dimensions is quite simply that all other things being equal a hull casemate plain has *more room* than any sanely proportioned turret. Case in point various issues with turret ring diameter tended to quickly come up whenever people tried to substantially upgun existing tanks.<br /><br />Conversely recoil forces do not somehow magically disappear when they reach the turret ring - they carry over into the hull and ultimately suspension and will rock and shift the vehicle all the same if sufficiently strong relative to its mass. IIRC this was a real headache whenever militaries got the bright idea of stapling a very powerful gun onto a very small and light hull, usually for airmobility purposes...<br /><br />Probably also worth noting that in the late Fifties the ISes started getting their old D-25Ts swapped out for fancy new M-62-T2s, and improved ammunition was designed for them in the Sixties. (Mind you IIRC the M-62 was specifically designed to fit in the D-25 mounting with minimal changes so doing the same to any ISU-122s still in the roster should've been easy enough...)<br /><br />As far as the 130 mm goes, though, I was under the impression the Army disliked the whole caliber for the exact same reason they'd been leery of the 107 mm - it was a *naval* caliber with no prior history in the ground forces, and aside from the usual interservice bullshit they REALLY didn't want to further complicate their munition logistics with those.Kellomieshttps://www.blogger.com/profile/04915110653443066212noreply@blogger.comtag:blogger.com,1999:blog-5030145265861917845.post-2680716857896133132020-07-26T12:51:15.331-04:002020-07-26T12:51:15.331-04:00Interesting article. First time I have read there ...Interesting article. First time I have read there was a shortage of A-19 guns. Most articles on the IS tank development claim the rejection of the DS-10 100 mm was justified by the "fact" that "by contrast, the Russians had oodles of A-19s lying around and ammo for them" which does not appear in fact true.<br /><br />But this article brings up other questions.<br /><br />1) Usually, tanks are considered superior, if higher-cost, alternatives to SPGs. Tanks are considered superior because of their greater flexibility, able to fight offensively and defensively, at close range and at long ranges, about equally well; while SPGs (lacking a turret) are at risk in close-range engagements and better suited for defensive or overwatch roles. The sole advantages of an SPG are:<br /><br />1) As the recoil of the gun is buffered by the entire chassis, not just the turret, the SPG can mount a larger, more powerful, weapon than its tank analogue;<br /><br />2) Lacking a turret, the armor protection of an SPG can be made superior to its tank analogue;<br /><br />3) SPGs are cheaper and easier to produce.<br /><br />With the ISU-122, advantages #1 and #2 do not hold. The ISU-122's gun is no more powerful than that of the IS-2, and I think it's safe to say that its armor if anything is worse. So its only advantage is lower cost (in terms of hardware, as each IS-2 only carries four people instead of five in the ISU-122, the cost in bodies for the ISU-122 is higher. And cost in bodies usually trumps cost in hardware). <br /><br />All armies went away from the turretless SPG concept after WWII, not just the Soviets, in favor of tanks. I do not understand why the D25 was considered "obsolete" postwar, as it was still being used in IS-3s and IS-4s, and improved version (D25A) making its way into the T-10, whose service extended throughout the 1960s. To me the only way to justify and 'rescue' the ISU 'tank destroyer' would be:<br /><br />1) Improve its armor protection, which was subpar for its class even by WWII standards. To this day I cannot understand why it was so impossible to slope that 90 mm plate at 50 + degrees, like the Jadgpanther had or the SU-100, which may involve reducing its crew from 5 to 4 (to me, also a plus). Maybe with a transverse engine design like that of the T-44 to reduce the load on the front suspension this could have done. Mind you, I'm not talking about building a 60- or 70-ton unkillable beast like the IS-4 or IS-7, just something that has a good chance of surviving hits from a weapon on par with the Kwk43 at ranges over 1000 meters, which would be the probable employment range of a SPG like this.<br /><br />2) Up the punch of the gun. To me the 130 mm S-70 was the logical candidate. It could destroy even well-armored targets at long ranges, ranges where such an ISU would be used, and packed a powerful HE punch as well. <br /><br />So in short, I think there was still a role for such an ISU weapon. I just don't see why the things needed to make it work weren't done or even attempted (save the Object 704, which kept 5 crewmen, and was only for the 152 mm version).Stewart Millenhttps://www.blogger.com/profile/01261690405884935161noreply@blogger.com