The 6 pounder is possibly the best anti tank gun in the game. Sharing a RoF of 12 rounds a minute, same as all the very small caliber early war anti tank weapons while not suffering the same drawback of low penetration. It's 175mm APCR stat at 12 RPM is crazy strong, but even its basic ammunition is extremely strong at 12 RPM. This gun alone arguably makes the Churchill IV the best tank in the game at its price tag, even considering the lack of HE rounds, just due to the extreme threat it poses to tanks even much more expensive than it.
I think the 6 pounder's RoF should be reduced slightly, perhaps to be on par with the Pak40 as it punches at about the same weight. This would help bring it into line a bit more as currently it performs ridiculously well.