T54 turret front is 23 in game terms. Not 20.
30cm at the muzzle, 29 at 500m, 27 at 1000m, etc as shown in the table for it at this site:
http://www.wwiivehicles.com/great-br...ion-tables.asp
Running the APCALC utility, it gives 30 at the muzzle for 20pdr 52 (presumably the Mk. 3 APDS), 27 at 500m, 24 at 100m. So its actually a smidgeon
under-performing in the game.
Final range bucket where armour pen equals the front turret of t-54 is 1200m. (If defending armour is equal to the pen value, it is
not a guaranteed pass-through). Also, on the game map the firer is not always at a 0 degree angle-off, so the effects of the target angle-off will usually reduce basic penetration somewhat.
The 105mm L7 1959 model APDS will do a T-54 front turret to 1500m using APCALC, again in perfect conditions.
The 20 pdr was a very good gun, but had reached its ballistic limits. The 105mm allowed more penetration at a longer range, but the main thing it really brought to the table was a calibre useful for chemical energy munitions (HEAT and HESH).
20 pounder centurions do about evens against T-54s at 1000m and under in the game, but the T-54 tends to plink a few of them back using the 3-5 HEAT shells they carry by the time the up-armoured models arrive. And they can do tat at long range too, which is annoying. Plus centurions are slow, so will often lose any manoeuvre battle against a thinking opponent. If trying to stop a horde of T-5X with Centurion III with the original armour suite, you
will lose quite a few..
The data wont be changed. 20pdr APDS was twice as energetic as the WW2 German 88L71 at the muzzle after all. It
was rather a hot gun. It is not a wonder-weapon, though.