So, I'm trying to do the quest you get from the Middle of Nowhere bounty board to collect the machine gun parts in the Salt Flats and I can't find the magazine! I've looked everywhere and I have all the other pieces.  Does anyone know?

Make it your active quest, it'll put your waypoint on it.  One of them (likely the magazine) is on top of a tower you must approach from behind and climb the debris to reach.

I'll have a look again, but putting it as your active quest just puts the waypoint in the the general location of all the parts. Thanks for your help.

I had an issue in the quest where you harvest the shock crystals where the waypoint was set in the middle of the first room in the caves and wouldn't move, even though there was nothing there.  The waypoints are the one thing that bug me sometimes in this game.

Look on top of the buildings, some objects you will need to look around to get them or under stuff...

Can someone tell me where this is? I've been looking for nearly an hour and can't find this one piece. This is my last quest too :\

DO NOT TRUST THE ACTIVE WAYPOINTS!!!  There are two pieces on two separate "gun part" quests that I've done so far which lead you to the wrong place. 
 
Either way, I haven't gotten to the Salt Flats yet.  I've been having to jump in with slightly lower-level friends the past few days and help them catch up a bit to where I'm at.  lol  I'm in Rust Commons still, but I've already been to Treacher's Landing (which was awesome).  I'm gettin' there.

Yeah I lost hope in the waypoints way back on my first 'gun quest', there's a thread around here showing it too as that's when I realized how these waypoints only steered my into the general area. 
 
All the same, I'm having terrible luck finding this damned Machine Gun Magazine, I've searched everywhere (except the one place I apparently need to be). I'm about to give up and work on another guy, hopefully someone else will find it and point me in the right direction so I can finish this damned quest.

It's on top of one of the huts in the area around the waypoint.

Guys, the waypoints sometimes aren't meant to lead you straight to it. In the Lost Cave the waypoint appears at the beginning because it's basically saying, "You're here, now go find them because they're pretty obvious when you see them." 
 
Same with the guns - the waypoints are set in a general area so you have the challenge of finding where they're hidden.

" DO NOT TRUST THE ACTIVE WAYPOINTS!!! 

The weapon parts are usually easy to find aside from one of the pieces. The last piece you try to find is usually high above ground or way down below, i found this and the sniper missing pieces frustrating as hell, but they are around. There is also a mission to find boxes of cigars, again, the last box was way up high and took me a while to find, DAMN you Borderlands!