Some maps designed for instagib are like that. You only get ARs or a really crappy selection of weapons because the mapper was lazy. It's easy enough to put weapons in most maps though.
There are two maps in the zip file for this map. The NW map stands for Normal Weapons and seems to have all of the normal DM weapons. The other map, LincolnCountyArena, only has shock rifles and is designed to use a weapon replacement mutator - but like most UT2003 mutators, it doesn't work as intended in UT2004. The mutator is supposed to give you Colt Revolvers. Instead it takes all weapons away including shield gun and leaves you with just a translocator - all you can do is telefrag which is kinda fun.