if the apc is made out of cardboard, yes.
I doubt a .50 bmg can cripple an apc
depends on the apc, but many can be taken out by .50 BMG
.50 BMG made with a hardened steel core can penetrate about about 25mm RHAe.
APCs are designed to take hits from the front and sides.
this means their top armor is generally thinner.
can you see where i'm going with this?
also, much modern armor uses ceramic, which tends to be brittle compared to rolled homogenous steel. .50 BMG, in armored combat, is almost always fired from a machinegun. this means that if one hit lands, you'll probably see a few - or a lot more - hit in around the same area. so it's got the crushing effect of a volley reducing the condition of the armor.