The bullet whistle point Raghorn pictured works okay and yes, its hollow. Depending on target/ground material one needs to clean it almost every shot and thats a pain - always unscrewing it. Anyways, I have seen (and heard) folks shot these on 3D-shots, quite contrary to the present trend of ever lighter tips, so I think it was an exception and just for the fun of it.
But, the one head which I found to be the closest in it's ability to whistle is this here:
Can it therefor be assumed, that a "Patriot" always makes the most noise ...?
Bowdoc,
I really like that 'last-chance' point :D Would you consider parting with one? However, I guess sending it might be difficult and/or you may be find yourself sacked for putting a letter-bomb on it's way
BTW Doc, the best German Luftwaffe equipment was just rebuild in your backyard. So you maybe had the pleasure of seeing her on her test flys whereas I had to wait until her first public display over here in 2006
edit: spelling