When I originally planned my Necromunda chaos cult, I knew I wanted a disciple (champion) with a heavy stubber. It was later suggested to me that a disciple with a long rifle would be fun. A high quality ranged shooter in Necromunda is always a useful thing, and a long rifle has pretty fun stats - S4 like a boltgun, positive to hit modifiers at long range (and the maximum range is long - 48"!). Not to mention the knockback ability which can hurl targets into other models, walls, or even off gantries.
It just so happened that back in 2015 when I was making some completely unrelated
chaos cultists in pink, I had criminally decapitated a Jes Goodwin skaven champion with a jezail. He had sat unpainted in a pile for over three years, so I took the opportunity to look at him a second time.