Edit: Yes I realize Sister's like to burn heretics and I did find one random image of a miniature (no info) with a very similar weapon but I cannot find the exact pattern. It definitely has a belt for Bolter ammunition and some kind of pressure line but that's all I got. Hopefully some Warhammer_40k lore God will step in and share the knowledge.
Edit: Yes I realize Sister's like to burn heretics and I did find one random image of a miniature (no info) with a very similar weapon but I cannot find the exact pattern. It definitely has a belt for Bolter ammunition and some kind of pressure line but that's all I got. Hopefully some Warhammer_40k lore God will step in and share the knowledge.