display sidechat when auto HMG ammo running low

I am trying to get a sidechat mesaage to show up when the ammo count on a Auto .50 HMG reaches a certain level but after an hour of trying all sorts of ifs, whiles and waituntils Ive got no where.

_gun = (gun ammo (currentWeapon gun));
waitUntil {(_gun < 450 )};
player sideChat "less than 450 rounds left";

Little help please?

waitUntil {magazinesAmmo vehicle player select 0 select 1 <= 50};
hint "Hunter HMG ammo low";

Thanks very much Iceman77!