Yes, the original one provided with the pack was mine(JMGBarrettM82), the model he uses is that model, just with minor additions like the holes on the front etc.
he said in readme:
I made the p3d model from the MACK's JMG Barrett M82. I modify it but I use the MACK's
model as guidelines. I also used other files from the JMG Barrett that somes come from FlipeR.
the P3D was used, not as a guideline or reference drawing but as the whole 3d model of the gun.
the main point is i wasn't contacted, you always contact the author.
and my version 1 is provided with his pack, which will then overwrite my version 1.1 if installed, so that's not acceptable.
feel free to use the model for your NTW-20, once i know and am credited i'm a happy camper
i've contacted him about the model, but the email bounced, i'll try again in a minute to see.