I haven't played around with this too much, but it seems like your gun will jam if you have played any automatic ranged techniques earlier in the chain, even if one or more manual ranged techniques intervene. Also, this terminology — ugh.
I was still getting jams even with a retro assault rifle ("Made from actual metal, this rifle is something of a throwback. Seems they might have known something back then, because the higher melting point lets you sustain a far faster rate of fire.") I guess it's the quality of the bullets rather than the capacity of the gun that's the issue with jams here.
I wouldn't be surprised if in bad cases you could get some kind of "jammed weapon" effect, but I haven't been able to make it happen yet if it's out there.
There had historically been a lack of chain 6 earthly ranged filler techs, so I'm always happy to see another one. It's still a little hard to get an empty clip until you have access to The Slags, though, both so you can get salvaging tools and so you have ready access to shotgun rounds or long clips to salvage. The ability got get empty clips earlier on might be interesting, but I don't have a solid suggestion about where to put them.