Looking at the excellent pic's provided by DTVPKING the MP43/1 has a tapered barrel but on the MP44 the barrel is stepped. Which barrel do you have? May be a little boring on the site hole and a little lathing on the barrel might get you there.1mm here and another 1mm there. But if you are going for correct parts on a correct weapon you might need to keep looking for the correct front sight.
Just my 2 centavos.