As Ed said, it depends on the plater. Why else would a hi end pen company, be it Mont Blanc or who ever, use a 24k gold finish, as was shown recently in a link in an earlier post here?
Mannie, the 24K plating on a Mont Blanc is about 10 times thicker than what we get on the kits we buy.
The thicker it is plated the longer it will last and the more it will cost.
The COST of the gold is negligible (in single digit pennies) for any plating we might use. We had a LOT of gold plating done, when Dawn did glass--each 1 foot square panel cost a couple bucks---mostly labor to hang the piece.
I know we try not to indict any vendors, here and I strongly agree with that policy. BUT, as long as there are "Apprentice" and "Funline" kits available in gun metal (or any other plating), we certainly should NOT EXPECT them to perform like their more expensive (and quality controlled) older brothers.
Both PSI and CSUSA have stated that these pens are built for the "price sensitive" market---sounds much better than "they are cheap--don't EXPECT too much!!!
So, as I have said before----AVOID universal statements: Gun metal is neither WONDERFUL nor HORRIBLE. It will provide the durability that was designed into it---which is a factor you cannot control nor evaluate with the level of knowledge we possess.
How do you get kits that are durable? Buy them from a reputable source that SAYS they will be durable.
If the source SAYS they are for the market "where price is the primary concern", they are TELLING YOU what to expect--NOT durability.