Heavy Tanks, again (Split)

I would like to compare the M26 Pershing to the IS2

 

Compared

In general the tanks were somewhat comparable in overall combat capability, but I’d rate the IS-2 as superior in overall capability.

The M-26 had a combat weight of 41,900 kg, and a 500 horsepower Petrol engine. HP/weight ratio was 11.9 HP/ton. Ground Pressure was 12.5 psi. The IS-2 had a weight of 46,000 kg, and a 600 horsepower diesel engine. HP/Weight ratio was 13.0 HP/Ton, Ground pressure was 11.5 psi. So overall the IS-2 has superior mobility. The diesel engine gives better range, but this is offset by the greater internal fuel capacity of the Pershing. 161 km range for the Pershing vs. 150 for the IS-2, although using external fuel tanks the IS-2 has a 230 km range.

In Armor protection, the Pershing has 102mm glacis plate at 44 degrees (90 is vertical), LOS thickness is 146mm. Nose or lower hull is 76mm at 37 degrees, LOS thickness is 127mm. The Mantlet is 114mm curved. The IS-2 has a 100mm Round mantlet, and late model IS-2 had, (I believe) 100mm glacis at 30 degrees for a LOS thickness of 200mm. The real difference here is the Glacis, since the mantlet is vulnerable in both tanks, so the IS-2 has better protection, at least assuming equal quality plates.

Gun penetration. When the M-26 was introduced, HVAP and T33 ammo was finally available. This boasted the performance of the 90mm gun substantially from the standard ammo available before then. The 90mm HVAP combined the high penetration of the 17pdr APDS with very good accuracy. The T33 was a Panther killer round, able to penetrate the Glacis of a Panther tank reliably at 1000 yards, much better then other western AT rounds. The Russian 122mm already benefited from good penetration abilities against heavily sloped targets, and of course it did more damage, it was also accurate, although the trajectory was not as good as the HVAP round. The rate of fire was lower, and fewer rounds were carried.

At 914 meters against a 60 degree plate, the 90mm HVAP penetrates 221mm, at 1828 meters 156mm. For the 122mm APBC BR-471B round, it penetrates 120mm at 1000 meters, and 105mm at 2000 meters. However, the 122mm round will get better as the slope increases due to overmatching effects, plus the standards for penetration are different.
http://gva.freeweb.hu/weapons/soviet_guns9.html
http://gva.freeweb.hu/weapons/usa_guns7.html

Realistically, both can penetrate the others turret/mantlet at normal combat ranges. The glacis would be a harder shot, depending on compound angle. I would give the edge to the Pershing here, it has more ammo, faster firing, and flatter trajectory with HVAP ammo, although this advantage disappears if you restrict the Pershing to more common AP ammo. The Pershing’s glacis was comparable to the Panther, and the 122mm could penetrate high quality Panther Glacis plates to around 600+ yards, poor quality ones at almost any range.

The HE round for the 122mm is much better, while the 90mm has more ammo (70 vs. 28).

Overall I’d rate the IS-2 better for the breakthrough role, with its better HE ammo, better mobility, and better armor protection. The M-26 has the faster firing main gun, HVAP ammo that is very effective in the AT role, I’d give it the edge in a pure tank vs. tank engagement, provided HVAP ammo is available.

Just my 2 cents.

 

Splendid post Eric45, welcome to the forum!

I've heard it said that the Pershing's engine was very unreliable, and that this coupled with the bad performance of the 90mm gun with anything but HVAP rounds made the Pershing a bit of a disappointment. While it is true that the Pershing carried vastly greater amounts of more easily handled ammunition than the JS2, only a minority of this provided the superiority in penetration the M26 potentially enjoyed. How much of its ammo load was HVAP?

 

What was the difference and variation?

 

Honestly, I don't know too much about that. I believe shortages of certain critcal materials used in armor led to pretty wide variations in the glacis plate quality of the Panther. I know, for example, that high quality Panther glacis plates should have been invulnerable to 90mm and 17pdr APCBC rounds, however, they did sometimes penetrate, (Although the only photos of pierced Glacis on Panthers on the Western front appear to be 90mm, not 17pdr, despite lower performance).

I may have been wrong about the range for a high quality Panther Glacis. Jentz claims that it couldn't penetrate even at point blank range, however, it also claims that the Panther had to be withen 100 yards to penetrate a M4A2 Sherman's glacis, which is nowhere near accurate.

This is the best I could find regarding the ~600 yard limitation.
http://www.network54.com/Forum/116312/m ... ed+AP+Ammo
Although I've seen this info elsewhere.

 

I don't know the postwar standard for ammo load out, I know that HVAP for the 76mm was in extremely short supply for Sherman tanks in WWII, maybe a round or two per tank, although they could trade with m-18 tank destroyers for more.

90mm HVAP was issued on a virtually experamental basis in the last month or so of the war. Had the war gone on much longer, HVAP ammo supply would have gotten better. I would guess that the AP loadout would evantually be split between the T33 round, which was better against heavily slopped targets, and the HVAP round. I would assume at least half the ammo load would be HE, plus some smoke rounds. By the time Korea came, HVAP shortages were no as big a issue. (One would hope not, after 5 years.)

Of course, I would imagine that a good crew would save the HVAP ammo for tanks that would require it, like the Is-2.

Operationaly the Pershing did appear to be a disapointment, although that might be because it was being compared to the Sherman, which had a reputation for being a reliable, hardy tank. It would be interesting to compare operational losses between IS-2s and M-26s, but I've never seen such information.

 

Would be interesting if there had been combat between these two tanks...

Sorry for the alternate history stuff...I just wonder how these two tanks would have fared against one another.

 

The crew would is an extremely important factor, Wolverine.

For pure machine vs machine comparison, see Erich45's excellent post.

 

Wasn't the IS-2 supposed to be very cramped, leading to a very slow loading time for that heavy ammo?

Tony Williams: Military gun and ammunition website and discussion forum

 

I wonder if they have met anywhere?

Korea seems most likely, but I have only really heard of T-34 tanks being used (along with all kinds of other AFVs, but no other actual tanks).
If anyone can enlighten me, please do...

 

In Korea, I think China had some IS-2's, but I believe they were never used in combat. Don't qoute me on that.

Thier respective descendants did meet, or should have at least. IS-3's were used in the middle east, and should have seen combat against Israel M46 (M26 with a more powerful engine), and maybe M47's and M48's? Not that that is very useful here.