I'm doing up an MP5 clone, and finding a decent barrel is getting to be a bit of a bitch.  I can't find any POF barrels, the HK94 barrels I've seen around are beat up, so it looks like my last option are the Special Weapons stainless barrels.  Are these worth using for a new build?  I hear about Bobcat and Special Weapons rifles needing 'hot' ammo to run properly, does this come from the barrels having out of spec chambers?

Their barrels are fine.

Their receivers are a bit out of spec.  breaking them in with hot loads helps to be sure the gun fully cycles in the early life of the gun.

I believe the barrels are US made, which is a big plus if building a title I firearm.

If you are looking for a 3-lug barrel, POF barrels are not quite to spec.

I have a SW5 barrel (full length carbine) I'll sell you for $125.  It is left over from when I SBR'd my SW5 and put a German 3-lug barrel on her.  It is complete with front sight.