i am not an ammo specialist, and seriously i believe that gary
is better in such area than me, just dont know where he is lurking
now.
back to your question:
1. M1 Abram MBT DONT use ERAs, in fact most (if not all) western
MBTs dont use ERA as extensively as eastern (read russian T-series)
tanks.
the american Abram and british Challenger tanks uses "Chobham
armor", which is a composite armor composed of layers of different
materials including steel, rubber, ceramic and "other top secret
stuff".
the abram was blessed further with the use of "depleted
uranium", a gift from the american nuclear reactors. the uranium
with its greater density makes non "uranium tip" sabot round looks
like "wooden stick". the penalty without doubt (due to high density
of uranium) is the massive weight, which prevents the whole abram
from being covered top to toe with uranium.
the leopard 2 tank uses perforated armor, somewhat similar to
the "chobham" concept with the addition of "space armor". which in
the opinion of some people is better then the original "chobham"
armor found on challenger 2 against both HEAT and KE rounds.
2. having said the above... your question is can APFSDS
penetrate a ERA.
ERA was developed as a counter to HEAT (high explosive anti
tank) rounds, against the APFSDS, its practically almost useless
(perhaps maybe add 10mm of steel armor, which is practically not
worth mentioning).
nontheless, the ERA does have its purpose, in a battlefield
flooded with HEAT anti tank weapons like the 84mm carl gustav,
MILAN anti tank missile and LAWs, it could prove a life saver.
but ERA is no good if the opponent uses the following"
1. top attack anti-tank weapon like the SPIKE.
2.HELLFIRE (heavy stuff fired from apache helicopter, even M1
abram also gets toasted).
3.APFSDS round from another tank.
4. anti tank mines.
5. tandem warhead anti tank weapon like the matador.
TUSK abrams uses ERAs in Iraq mainly to against RPG7 or
equivalent shape charges.
