I think it’s worth bearing in mind that when Marx wrote that, guns were still using powder and percussion caps.
The Gatling Gun predates came out a 5 years before Das Kapital. Sure arms hadn’t had the revolution they’d get during WW1 yet, but they were plenty capable.





Marx made regular writings and letters to contemporary movements up until his death. At no point did he back down on violent, sudden revolution as the path to achieving Socialism. Marx was many things, but he wasn’t anti-gun.