If you see random numbers smaller than 25 in the following text (which are not marked as weight values or other stuff), then it probably are footnotes. I wrote my answer in some text editor because I did have internet connection troubles. There I used the footnote-function for my sources.
So their claims are completely wrong. M1A2SEP was fielded in v1 variant in 1999. M1A2SEP v2 had more improvements to it's FCS. And currently whole M1A2SEP fleet is made from v2 versions that were fielded around 2010.
Actually they are right. The contract for the SEP v.1 was made in 1995, but the first serial tank was delivered in 1999 - this matches with what they claim. I just assumed that the U.S. didn't order a serial production without any pre-series vehicles.
Could you please provide a source that all M1A2 SEP v.1 were upgraded to M1A2 SEP v.2?
If You call this major modernization... then I really not know what to think. Don't know how this is made in Leopard 2, but in M1 if You have new ammunition, the only thing changed in FCS is ammunition ballistic data memory card.
The whole gun system is modified, it has a new barrel, a new recoil mechanism, a new gun mounting, new gun and turret drives, new stabilization etc.1 The commander has a night channel, the system now also accepts the first laser echo to engage helicopters and the FCS got an electronic shooting mode for faster engaging.
The computer per se may have stayed the same as previously (which is honestly a thing I don't know), but the computer now has to work with a large number of other components. According to the Swedish manual from the FÖRSVARETS MATERIELVERK the Strv 121 (Leopard 2A4 loaned from Germany) had a GE8109A029 STN ATLAS ballistic computer, while the Strv 122 (Leopard 2A5 version) has a GE8109A039 STN ATLAS ballistic computer... so it seems that it was replaced.
Day channel is not nececary for CITV, 2nd generation FLIR gives very good quality image. Besides this CITV is part of system, not just a commander periscope with thermal camera. I know that
The very good image quality is something I don't doubt – however if two countries have similar equipment on the battlefield and only one of these two countries is you enemy, how do you see the differences between them? It doesn't matter if a T-72 has a woodland camouflage pattern or is pink coloured, the thermal imaging system will show you exactly the same thermal signature.
It's also the same with the infantry – you can engage them, but you cannot be sure that they belong to your enemies. A day channel gives you here the great advantage that the commander does not have to use his sight blocks (which have a very limited usefulness on long ranges) or turn the whole tank turret to the detected vehicle/infantry.
I completely not understand mentality of Germans. Instead of making progress, finding the best solution, they seems to be happy with outdated sighting system. Tank need to be well prepared to fight in all conditions. Even in Afghanistan, sigthing system in M1 series gives better results because even as a stationary outpost, tank can detect, identify and eventually engage targets like groups of insurgents. So better sighting system is allways better.
The outdated sighting system works perfectly. The "outdated" EMES-15 still has the same magnification than the M1A2 SEP without digital zoom – and a slightly better than the previous M1 and M1A1. When it comes to day channels the EMES-15A2 (which also has a 4x daysight channel) outperforms the gunner's sight of the M1 and M1A1.1
I don't know if the System Enhancement Package includes new daysights or not, but if they are just better than the ones of the M1A1, then it is not a very large difference between them and the EMES-15A2... but I have never read that the day channel of the gunner's sight was changed.
The main point speaking for the German FCS components and the EMES-15 however is their performance. CAT shooting and the Greek trials show that
As for targets identification, Americans do not need normal day light target identification. They have CIP's and FBCB2/BFT system, so commander of each vehicle, can check position of other friendly and detected and marked enemy vehicles on map that shows also his own position.
That's nice if they are operating alone. But if they are working together with another country, which doesn't have FBCB2/BFT...
Let's say the U.S. would invade Iran after the Iran went to war with it's neighbor countries... how would they U.S. tank commanders find out if the tank they see is a Iranian T-72 or from another country?
Leopard 2A6EX is non existing, it was technology demonstrator, nothing more.
The Leopard 2A6EX served as base for the Leopardo 2E (Spain) and Leopard 2A6HEL (Greece). Features like the increased protection at the hull and the turret roof, the air-conditioning system, the APU and some minor stuff were passed from the Leopard 2A6EX to the Leopardo 2E and the Leopard 2A6HEL.
Btw: There were two demonstrators.
What makes You think that M1A2SEP is not better protected?
In this document it is clearly said that recently M1A1SA and M1A2SEP recived frontal and side armor upgrades. How do You know what is empty and combat weight of these tanks right now? I don't and Americans seems to not be very keen to share such data for these newest variants."
The combat weight of the M1A2 SEP v.2 is 69.29 short tons.1 Converted to metric tons this is 62.85 metric tons. The combat weight of the SEP v.1 is 68.57 short tons, which equals 62.2 metric tons.2 Also note that the source does not mention that the protection of the SEP v.2 is higher than that of the SEP v.1, but says "The M1A2 SEP has improved frontal and side armor for enhanced crew survivability" - there is no indicator that the SEP v.2 utilizes newer armour than the SEP v.1.
The combat weight of the Leopard 2A6 is 62.4 metric tons,3, 4 although some German websites claim a lower value.5 The Strv 122 has a combat weight of 62 tonnes,6 so the Leopard 2A6EX will probably weigh 64 tonnes.
Even if the Leopard 2A6 weighs only 60 tonnes as claimed by panzerbear.de, then it still has a turret weight of 21 tonnes – according to various sources the turret of the M1A2 SEP will weigh ~22 - 23 tonnes.
I don't have values for the exact empty weight, but the M1 typically carries more stuff external and also has a greater interior volume – so it also can carry more stuff internally. It seems very unlikely that it has less non-armour weight than the Leopard 2.
If the armour is more weight efficient, then not by much – I haven't seen any real improvent without increase of armour thickness... there are improved steel alloys and improved ceramic tiles, but these does not offer a too high increase in protection – using these the cost increase very fast. AMAP for example is very mass-effective, but for reaching a higher level of protection than previously you need in nearly all cases a thicker armour... the density of materials was decreased to improve performance.
I cannot see that the SEP v.1 (nor the v.2) has thicker armour than the M1A2, and the same can be said about the SEP v.2... especially since your source did not mention that there is difference in armour between M1A2 SEP v.1 and SEP v.2.
Most forms of very mass-efficient armour require an increase in thickness. ERA, NERA as breaking stage, etc. Still it seems likely that they uses more mass-effective armour than the M1A2... but this does not mean that it is better than the Leopard 2A5.
I don't doubt that the M1A2 SEP has stronger armour than the M1A2, but I doubt that the M1A2 has the same level of protection as the Leopard 2A5/6.
Here is a small (and very rough) sketch which does not represent real armour thickness and dimensions:
The left side shows the Leopard 2A6 turret layout, the right one the M1 Abrams. There are now four reasons speaking against the M1 being better protected at the same weight (and level of technology):
1. the turret of the M1 is wider and therefore it has a larger frontal profile – with the applique armour both tanks have similar frontal profiles, but there is less surface under full armour protection on the Leopard 2A6
2. the M1 Abrams carries composite armour over the full side – the Leopard 2 has only a very small side area which has to be armoured, most of the turret side is covered by the front and the less armoured bustle
3. the Leopard 2 has a thicker armour (even though it is hollow), i.e. more space to interact with the projectile, there is more time in which the fragments of a projectile can spread
4. the turret of the M1 has more internal volume – which means that more of the weight is not located in the armour (for example the roof weight)
See: You claim that the armour of the M1A1 and later models is 960 mm thick. However you are alone with these claims... I measured drawings – they show less armour thickness. I took a look at Russian forums and websites – they claim a smaller armour thickness. I took a look at wikipedia – they claim a smaller armour thickness there. This does not mean that you are wrong, but believing in you without proof or source is unreasonable.
There is some interval of armour thickness: 820 mm,1 850 mm,2 880 mm3 and 960 mm. I will not believe in the extrema without any reason – the middle values are closer together and they are reasonable if we take a look at other vehicles.
For the Leopard 2 there was also such an interval: 650 mm,1 800 mm,2 ~1000 mm3. In the end the middle value was the most correct and from looking at other vehicles it was also the most reasonable. And for the T-90 there are also various sources putting the armour thickness at 800 to 950 mm...
I often use google for gathering information if a topic interests me and I don't have any book about it and I am too lazy to go to the library. While googling I often find your older posts on militaryphotos.net etc. were you wrote that the Leopard 2 must have thinner armour than the M1 Abrams and possible has 500 – 600 mm thickness. This seems to be some dogma you believe in: "the M1 is having better armour than all other tanks".
You said that some Pole in American service wrote to you that it is ~900 mm... but still you made it 960 mm, while other estimates (880 mm for example) are way closer.
Not to mention that saying that Leopard 2EX or upgraded ones have thicker hull armor is pure manipulation and lie. Lower Front Hull is thicker in M1 series, while the glacis plate have variable thickness, ~50mm over driver station, and ~80mm over rest of glacis plate surface. I proved this with photos. Besides this, frontal hull fuel tanks also acts as additional spaced protection for hull front.
"[M]anipulation and lie" in your fantasies maybe. But the truth is that only you claim that the hull armour of the M1 Abrams is so thick (~740 mm). Nobody else says that – not the Russians, not the Americans, nobody. But you keep claiming that. If you have a source or a proof for this claims then I will accept these, but currently you have nothing to proof that. Nearly all other MBTs, regardless from which country or generation have a different armour layout, where the turret is thicker armoured and the hull has less armour; but the M1 Abrams is the exception?
And all line-drawings from the M1 Abrams are wrong? I mean you and militarysta did measure the armour of tanks via drawings for – this way you came up with estimations for all tanks except the Leopard 2A4, for which you have images of measurement on the real vehicle. I have no problem with you estimating protection via drawings – but when it comes to the M1 Abrams then all images are flawed or intentionally manipulated? With these claims I have problems.
I think when it comes to you and the performance of the Abrams armour and firepower it is often more wishful thinking than facts.
The glacis plate per se of the M1 Abrams is as you said approx. 50 mm over the driver's station and approx. 80 mm over the fuel tanks. I don't have a problem with this claims as you provided proofs. But the Leopard 2 with hull applique armour has there even more armour – the applique armour has been fitted to the whole glacis. Even more relevant is that the armour is non-homogenous, it is composite armour.
The lower hull front of the M1 series is not thicker than the Leopard 2 armour. It covers more of the lower hull front, but I cannot see after looking at over a dozen images that it would be thicker. The Leopard 2A6EX and some other variants which are fitted with applique armour seem to be thicker armoured at the hull front.
Gas Turbine engines can use different liquids as a fuel, only if these liquid can be spread in combustion chamber and will burn but still, JP8, diesel fuel, gas, alcohol, everything can be used by such engine. It is still a gas guzzler but it works. In fact the problem of gas turbines is that work for more fuel efficent engines of that type were cancelled. It is a pitty because Gas Turbine have much more interesting capabilities and future perspectives than a Diesel.
The engine of the Leopard 2 runs also with other liquids than diesel – but not with all and not with so much as the gas turbine. Also not all types of burnable liquid can be used on the M1's gas turbine... if you use the wrong fuel this can lead to waxing or damages of the engine.
I suspect it is because that idiotic approach of European countries to DU, Americans probably took their own DU ammo, and had ballistic data for WHA ammo, so they needed to take KEW WHA APFSDS from Egypt.
You are aware that the Abrams tanks of Egypt were using the KEW ammunition and therefore the data for these rounds was available to the Abrams? And why should the U.S. put the ballistic data for the M829 APFSDS series in a tank which they want to sell to Greece who then would have to use the KEW ammunition?
This doesn't make sense. The M1 Abrams scored pretty high in FCS trials and in at least one category even outperformed the Leopard 2 (which missed once) – so I don't really see where and why there should be a problem with the FCS and the ammunition... because the M1A2 didn't score best in all trials?
There was problem with propelant charges AFAIK. They took propelant for L11 gun and ammunition for L30. Someone ----ed up preparations for trails. It was not fault of FCS that is preatty good one in CR2.
Can you provide any source for this? I have heard that they had the right ammunition, but it was stored wrong so that it exceeded the shell life. Something similar happened in the past years in Germany with pistol/rifle ammunition (at least according to a German forum) – the ammunition was stored not under the right conditions and therefore an amount of it is flawed. Now a few workers have to take every single bullet of the faulty stored ammunition out of the box, examine it and if it is not flawed but it back into the box. Very stupid work.
However I think that militarysta is correct. If the T-80 or T-90 fail to win a competition, then it is because they are bad. But when some tank like the Challenger fails, then it is because of some other influence and not the fault of the weapon system or the crew.
The thickness is almoust the same. Of course some error is obvious but it will be max 5-7mm so this plate have etween 50,4 to max 57mm but there is no possible to have 80m thick there. 
