Hi Fabricio,
Everyone is pretty much correct in their responses
. Here are some more details.
The MP43, MP43/1, MP44 and the StG44 are essentially the same weapon, minor differences as follows:
1. MP43/1 is the same as MP43 but has a screw on type grenade launcher rather than the clamp on type used with the MP43.
2. There is no apparent reason for the change in nomenclature from MP43/1 to MP44. Most MP43/1 rifles have the V-type telescope mounting bracket on the right side of the receiver; some MP44s have this bracket, but no MP43s have been found with the bracket
The change in nomenclature to StG44 was politically inspired, but 'Assault Rifle' (StG Sturmgewehr) is more truly descriptive of the role of the weapon than is 'Submachine Gun' or Machine Pistol' (MP-Maschinen Pistole).
My reference for the above, is 'Small Arms of the World' by Edward C. Ezell.
Have fun with your project, and should anyone question or give you grief as to your description, you can impress them with your extensive firearms knowledge
!
Joe