As a standard AT gun, yeah, the m1 57mm is the best.
I disagree. 57 is good on axis because it's low penetrate doesn't mean much vs allies low armor tanks. So it's characteristic (low pen / fast shot) works good.
OTOH, allies would die to get pak40, thx to it's good penetrate & good skill that can stun the tank with vet1.
Someone mentioned raket is bad because it can hardly penetrate kv1/comet/churchil, but in reality raket has higher penetrate than 57.
(57: 150/140/130 vs raket: 200/190/180)
Thinking about it, OkW p4 or vet2 OST p4 has 234 armor which is only 6 less than churchil. Panther has 260 by default and goes up to 286. It can bounce almost half the shot even at the close range. So... You see what I mean. 57 isn't the best at least on the hand of allies. Whom need high pen to deal with high armor tanks. I'd rather use 6pounder on this matter.
However, I'm happy with where raket is in current patch. Raket surely was OP when it had both stealth move & retreat. But now it can't do stealth move, and it has less range than other ATs.