[JaM]

1.All my esstimates are from Collins page.He has them from Tanknet or other sites.Most of them are estimates of Paul Lakowski(Merkava estimates are his job)
2.As I said, Merkava Mk3 is complete new tank.It shares composition, engine in front,etc... but it has modular passive armor instead of spaced armor used in Mk1 and Mk2.I have compared composition of Addon armor from Leopard 2A5 becouse, Israelis cooperate with germans.Germany used their APFSDS for 105mm cannon (M111 = DM-23,M413 = DM-33 etc)Leopard(2A5) use perforated addon armor + composite inserts and rubber (there is quite good discusion about it on tanknet now - armor sientific section)Similar composition you can see at photos of Mk3B.
3.Front Glacis of M1 Abrams was really enough against threats in late 70s early 80s.Sloped plate was able to deflect most of soviet APFSDS, HEAT rounds were allways deflected as critical angle for HEAT is around 75°(Tanknet, Paul Lakowski).ALL Soviet APFSDS rounds from 1970-1989 were sheated - steel penetrator with tungsten or DU core.Becouse of that, they were not so effective against Spaced armor.First Soviet monocrystal APFSDS was BM-42.Last sheated US projectile was 105mm M735 (1978).
Critical angle for APFSDS rounds with L/D 10:1 to 15:1 is around 80°.Longer rods, better effectivity against sloped armor. Round with L/D 30:1-37:1 will be not deflected due to slope at all.
4.Merkava Mk4 will have an edge over M1A1 on long ranges.It can fire LAHAT top attack ATGM or use APFSDS rounds. Egyptian M1A1 dont have DU armor.They are in 450-500mm KE region, so they would not survive APFSDS hits (Most of modern APFSDS rounds could penetrate 500mm armor at 3000-4000m)