120mm L27A1 APFSDS
There seems to be very little information about the CHARM projectile. I managed to get this little bit of information from Janes.
"L27A1 APFSDS projectile This is known as the CHARM 3 APFSDS, with a greater DU penetrator length-to-diameter ratio than earlier models, and is thus "significantly more effective". Integration development of the CHARM 3 round began during the early 1990s but was delayed from 1997 onwards by a lack of ranges suitable for firing trials within the UK. Even so, the L27A1 APFSDS became available for service with British Army Challenger 2 MBT regiments during 1999, ahead of the planned schedule. The L27A1 is fired using the L16A1 CCC.
By the end of 2001, the British Army was said to have acquired its full warstock of L27 rounds and associated L16/L17 (desertised) charges. Further production seems unlikely, since the propellant was manufactured by RO's Bishopton facility (since closed) and the penetrators were machined (from US-supplied blanks) by RO Speciality Metals (scheduled to close in the near future). The propellant charges will shelf-life expire about 2015.
A competition to provide a CHARM 3 training round (C3TR) for the L27 was won by RO Defence at the end of 1999. The 120 mm C3TR consists of a charge and a saboted projectile assembly and, following development, is manufactured at Birtley and Glascoed"
Hope this is of some use to you,
Cheers