Is ballistol harmful to guns?
Would it ruin stainless steel revolvers? Would it ruin polymer guns?
Ballistol will not harm guns, not stainless steel guns or polymer guns and not revolvers.
I wouldn't apply it directly to wooden grips/stocks, but other than that I wouldn't have any problem soaking any of my guns (including the ones that are nickel-plated) in Ballistol.
1. The fact that Ballistol claims to dissolve "traces of copper, lead, zinc and tombac" does NOT mean it dissolves "all soft metals", as the video maker claims. It certainly does not mean it dissolves gold.
2. The fact that Ballistol claims to dissolve TRACES of some types of metals does NOT mean it's going to consume those metals wholesale if it makes incidental contact with them.
3. As mentioned, the video maker's assumption that all nickel plating is plated on top of a strike coat of copper is incorrect. It is possible that some nickel-plated guns have a copper strike coat, but it's the exception rather than the rule these days.
4. Merriam Webster gives one meaning of "vault" as "a room or compartment for the safekeeping of valuables". It is quite a stretch to say that a safe isn't a compartment for the safekeeping of valuables.
The video is a 7:09 waste of time for anyone who watches it, unless they can get some entertainment value from it. It's certainly not useful as an informative source.