Like President Bush, The Arizona rifleman is travelling Europe, and he has a question:
"Singapore had a contingent of guards at the [Buckingham—DF] palace (...) The Singaporean troops were carrying chrome- or nickel-plated M16A1s, which struck me as a bit weird. Does anyone know if these rifles could be functional if so plated, or if they're only suitable for parades and whatnot?"
I can't think of any reason why a chrome-plated barrel would disable the gun. I'm quite sure however that it would make it quite unpractical for anything that requires event the slightest degree of "discretion" and camouflage. And, oh boy, cleaning the piece must be something else.
The Guard at Buckingham is, with all due respect, quite a spectacle indeed--so much so that it's easy to overlook the fact that these guys are nevertheless the Queen of the United Kingdom of Great Britain and Northern Ireland's guards. I'm fairly certain that they're not selected and tasked there just because they can stand to attention looking pretty.
Considering how Europe's monarchs, all over the ages, made it an habit to pick up elite troops as their close guard, I'd also risk the guess that glittery M16A1s or not, it would be a most unfortunate idea to try anything funny at those Singaporeans guards.
As we wish the Arizona shooter an instructive, and even possibly pleasant trip around Europe, let's conclude with an amusing historical fact in that respect. When the Allied powers of the time first managed to defeat the proto-fascist Napoleon (so-called "great Emperor of France and General of Europe"), he was granted a personal guard of several hundreds men to join him in his exile on Elba. Ironically enough, the man who is still worshiped by most French (including high profile ones, like the infamous de Villepin and the frantic space-wasting gnome Sarkozy) picked up a squad of Polish Uhlans (light cavalry) as his personal bodyguards—Men made of the same steel as the 87 that charged 9,000 Spaniards and 16 guns dug in at Somosierra Pass. Apparently, even the "Emperor of all the French" wouldn't trust his own kin when his personal safety was at stakes.
After the abdication of the "great Emperor of France", the last and short-lived old school monarch Louis-Philippe, King of the French, created another elite unit: the Foreign Legion that still lives and fights on to this day, at the tip of France's spear.
Don't tell me you can't see a pattern here.