The short answer...
In 2005, the BATF banned importation of any frames, receivers, or barrels for firearms that would otherwise be prohibited from importation if assembled. Note my emphasis - now rifle barrels were in the ban list, a departure from the long-time frame/receiver "non-sporting" clause.
The effect was immediate, and had wide-ranging repercussions. The first to feel the pain were folks here in the States assembling FN-FAL and AK semiauto clones - their source of barrels basically dried up.
HK got caught in the fray, because their 416/417 uppers and barrels were made overseas, and per the new BATF barrel ban, couldn't be imported for civilian sales. Military and law enforcement got an exemption, but Joe Sixpack couldn't legally buy one.
People got very indignant about it, and blamed HK for being snooty and elite, when it really wasn't their decision not to sell them here - it was the BATF's.
What the AK and FN-FAL folks did was create a domestic source of barrels. Now HK is supposed to be doing the same, and once those 416/417 barrels and uppers are made on U.S. soil, the onerous ATF import ban is summarily bypassed.
In the meantime, the few specimens that made it out of HK hands into the civilian population are considered hotter than a $5.00 pistol, and HK has been trying to get them back into their inventory. Without military paperwork or law enforcement department letterhead attached, I wouldn't touch one with a 10-foot pole.
