I am interested in buying a AR15 upper with a 14.5" barrel with a muzzle brake long enough to make the barrel 16". Is this legal? If so, any ideas on a vendor? I'm looking for a reliable weapon as light as possible.

the short answer is yes, providing the hider/brake is properly (perminantly) attached.

Bushmaster can hook you up with exactly what you want.  Call them and ask them about permenantly attaching a muzzle break to their M4 upper to make the length 16.1".  Make sure that the upper is post-ban if you only have a post-ban lower.

Check out Kurt's Kustom.  He just did a 14.5" Bushmaster w/A3 brake for me and it looks and shoots great.  It brings the length to 16" and is permanently attached.

[url]http://www.kurtskustomfirearms.citymax.com/albums/album_image/42611/4044.htm[/url]

Is a muzzle break legal in Kalifornia (more  specifically, the Bushmaster AK muzzle break) ? I have a Fab-10 lower (10 round legal thing..) and am looking at something similar with the permanently attached muzzle break.

Get a flashider for that fab-10 [;D] its totally legal..

Check out the new chrome lined M4's with Brakes from Pete in NH.  He can put a custom one together for you and they are very high quality!

Put a Flash Suppressor on that FAB10!!
And put on a telescoping stock while you're at it. I have both. This is totally legal under the national AW ban and in California. Hey, at least you can have a bayonet on the FAB10, so you're not totally defenseless while splitting open the rifle for reloading.

So as long long as a flash hider is permanently fixed to a barrel for a post ban lower it's legal???  I can live with that.

NO NO NO NO NO NO NO!

If the gun is post-ban and accepts a detachable magazine, you can't have a flash suppressor at all - permanently installed or not - as long as you've got a pistol grip on it.  

Remove the pistol grip and replace it with one of those evil thumb-hook things, and you could have the flash suppressor, and it wouldn't have to be non-removable.  However, you can't have a plain old GI A2 style flash suppressor, or anything else with a 22mm outer diameter, because ATF also considers those muzzle devices a grenade launcher.

If the gun does not accept a detachable magazine, you can have a fixed or removable flash suppressor, and a telestock, and a bayonet lug - go nuts as long as you keep the barrel length over 16".  

Since the FAB-10 has a FIXED magazine, it is not subject to the features ban under 18 USC 922(v), although in places like Californistan, there are some additional restrictions which the Caliban regime requires you to follow if you live under their harsh rules.