I created an addon for the v18 SSG. There is two versions. The regular one has hinges visible while reloading. The "authentic" one has no visible hinges like in v18
To use this skin, run in this order: Brutalv21.pk3, BD_Classic.pk3, BD_Zandronum_compatible.pk3 (for zandronum users), v18_SSG.pk3.