Only use APCR if you cannot penetrate anywhere on your target (KV for example). APCR is also really only effective at shorter ranges. However, if you are using the Panzer 38, you should be able to penetrate almost anything in the same tier with the APC rounds... which have some explosive element to them. I recommend using those mostly. See here for details: http://www.theskjaldborg.com/index.php?threads/official-ammunition-guide.8702/