I'll take a shot at this , because i've ask the same thing. I have the jordi rubio kwk 43/2/l71 in front of me. This is the "early type" one piece barrel. The difference between the two is "2" is a smooth barrel[one piece]. The "3" is the later "two piece" barrel, with a reduction in it. I have a pic. in front of me that has both type guns on two porsche turreted king tiger's. I can't remember seeing one piece barrel on a henschel turret. That is not to say there was not, but I would use the kwk 43/3L/71 because in the squadon cat this seems to show the two piece in the pic. The one piece was harder to make than the two piece is why the later ones were two piece, I think. Also i believe the kit has the two piece type in it.