So I've done a lot of side quests, played over 40 hours, and as I've been helping out the NCR and being not so nice to the Legion, I decided to follow that end path (NCR) with the first part fo the quest being to recruit the help of the Boomers from Nellis Air Force base.
Now I had been near there previously and spoke to the NPC George on the road to buy the "cheat sheet" on how to get through the artillery fire. Pretty simple as you need to hide in each house then make a run for the fence and follow that to the gate.
As I hadn't been there for a large number of hours I thought it was time to visit the Boomers so I fast travelled to the nearby shack. Only problem is that the artillery fire is now starting when I walk up the road (near the NPC George, which kills him). I thought this was weird and a crazy glitch but I figured it would stop once I make it to the fences and the gate.
I thought wrong.
This wasn't easy and when I got the the fence the artillery continued to fire. I then barely made it to the gate, and the guard there gave me the spiel about what did i want etc. Once this speech finished and he was gonig to call their leader, the artillery still continued!
And basically killed the guards and then me.
I reloaded a saved game from 8 hours earlier, fast travelled to the road leading to Nellis and same situation, artillery firing waaaaaaaaay too early.
So basically my game is broken and I can't finish it the way I intended.