I solve Birds of feather the non-violence way yet I am now being attacked by all Van Graffs associates. This is annoying. I choose the non-violence way so that I can keep Cass around while also be able to browse their wares. If I had known that there are no pratical way to prevent Van Graffs turning hostile after Birds of feather I would not have done that quest. My character depends mostly on his energy weapon skill and dispises conventional guns. Now that the Van Graffs are hostile how do I re-supply him?

[UPDATED]I found this http://newvegas.nexusmods.com/downloads/file.php?id=40742 at newvegasnexus that should fix the problem. The author also advice to use the console "SetAlly 1b2a4 118368 1 1 ;Neutral" to return the Van Graffs to neutral instead of installing the mod.

But why aren't there are any in-game warning of the consequence? The Van Graffs have some exclusive energy weapon mods and some unique GRA weapons. They are a essenstial to players who prefer pew-pew over bang-bang. Obsidian should have let the Gun Runner take over their inventories.

I tried every way to do this quest and stop the van Graffs from going postal. As of the last patch, this is the way that it is.

http://fallout.wikia.com/wiki/Heartache_by_the_Number

Now, your energy weapons needs are to be taken care of by the Brotherhood of Steel, as long as they like you.

Heartache by the Number is the quest and as CCNA said, all of your Energy Weapon needs will be supplied by the Brotherhood. It wouldn't make sense that the Gunrunners would take over the Energy Weapons business since the Van Graff's are still around, though you might as well kill them and loot their store.

I shot the crap out those Van graffs and the energy weapon supplies u need u get it from the brother hood of steel .

Ok, thank for the info. Does the BoS sell [GRA] stuffs as well? There are some rather expansive [GRA] gun that I could not afford to buy right now from Silver Rush. Will the BoS sell them later if I kill the Van Graffs?

The Gunrunners should sell them after you kill the Van Graff's, though you'll probably have to wait a few days for their stock to reset.

Old World Blues and the fiends are a good source of Energy weapons.

You could go to Quartermaster Bardon which is what I do. He sells Energy Weapon ammo in the hundreds. Once I bought 1700 Electron Cell Packs in one go.

I lay traps with their own mine and then kill them all.
Buggers are murdering innocent caravans and helping the legion... more then enough evidence for me to take them out.

Well actually...