UPDATE PART 2, SON OF UPDATE (THIS TIME IT'S PERSONAL)
I'm now well past 5000+ rounds, and pretty much out of 9mm so I figured it was time for another update.
Still running like a raped ape with outstanding warrants. It's been at least 3000-3500 rounds since I had a malfunction, and those were probably mag related. Running almost exclusively 124gr, mix of GECO and Speer Lawman for the most part, through POF and MKE mags. While I have some HK mags stashed away, I've been stocking up on POF mags as they're plentiful and only $30 a pop- 100% reliable and seem very well built (plus growing up during the 1994-2004 AWB makes me a total mag whore). Speaking of whores, it blows through mags like your ex-wife went through dudes on your last deployment... yeah, that fast.
WEAR AND DURABILITY:
The extractor spring is still working great and doesn't seem to be nearly the issue people make it out to be. Then again I'm running good ammo, mags, and under clean conditions so it's not exactly a hostile environment. I haven't noticed any excess or unnatural wear either. There's a small area near the ejection port where the finish is starting to wear from brass impacts, but even that's kinda hard to see unless looking for it.
I finally checked the bolt gap, and after 5000+ rounds it's at .016, which is really impressive. I didn't check the gap when I got it, but it's supposed to be around .018 new. It's hard to find a definitive set of numbers for the low end, but I've heard anything from .010 to .005, so clearly it's holding up well and has a lot more life in it.
MAINTENANCE AND CLEANING
I've been using Fireclean to lube it the whole time and it seems to be doing well. It stays as wet as your mom during Fleet Week and is just as dirty after (but unlike her wipes clean for the most part). Only a few places build up carbon, like the bolt head. I've read in the SMG experiences thread that a lot of people have had issues with MP5's if the bold head isn't kept clean- but I didn't even notice the carbon build up until about 2000 rounds through it. I usually clean it after every range session with a brass brush and a little dental tool action, it only takes a minute or so.
Before (this is only after 4 mags, it's usually much worse):
I take off the flash hider and clean out the carbon on the muzzle every 400-800 rounds to keep it from building up to the point that it might "weld" on the FH or effect accuracy. I always put a bit of Fireclean back on the FH and the 3 lug, and so far it comes off pretty easy. The muzzle on the other hand, not so much. For some reason carbon builds up there quickly, FH or not, and can take a bit for elbow grease to get off (that's what she said?). I just take off the thread protector and use a brass brush and boresnake.
Roller locked guns are kinda known for sending brass into low earth orbit, but the MP5 doesn't seem to be nearly as bad as it's 7.62 and 5.56 counterparts. Kicks it about 15 feet or so to my 2 o'clock, with some mild to moderate denting.
But does it flute? Oh fuck yeah, it flutes HARD.
Ok ok, those are pretty weak examples, they get a lot more obvious as the gun gets dirtier. Not a big deal, and helps keeping that asshole next to you at the range from claiming it's his.
IT'S NOT A CLONE FOR FUCKS SAKE
I frequently hear the MKE made guns are clones, as only HK made goodness is the real deal.
EAT. A. DICK. Seriously. It's license made under HK guidance in a real military national arsenal, that have been making MP5's for years. Sure, it's not as pretty in some ways as a HK made one, nor does it have the resale value. But it does have this:
What are you looking at? 2 things civilian HK guns don't have: a paddle mag release and it's a true 2 pin lower. Yes, you can add an aftermarket paddle release (and trust me you'll want to, changing mags without it is awkward as fuck), but it'll cost you a bit more scratch. And while the 2 pin lower doesn't effect function, it's how real MP5's are set up. The more you know...
Yeah, that's right- you didn't think you'd get a book report when you clicked on this, lucky you...
Heckler & Koch's MP5 Submachine Gun by Frank W. James
Long out of print but still able to be found, this is full of decent info on the history of the MP5 as well as some very dated training tips (this is from the early 90's). More of a detailed source than the other, the author clearly knows his shit and went through official HK MP5 training stateside so it's very thorough for it's time. It's also a nice time capsule to show you how much things have changed since then, with some very cringe worthy pictures of US Law Enforcement chicken winging, using drop legs, and a lot more pre GWOT stuff.
The MP5 Submachine Gun by Leroy Thompson
Much more current and better info on international operational usage than the previous book, just less technical details. It's less user level info and more international military and law enforcement history but still has a decent background on how the MP5 came to be (Teutonic SMG Messiah?) and it's different variants. It's also got some pretty cheesy "in action" illustrations for your inner 12 year old. Also still in print and fairly easy to find.
GSG9 German Response to Terrorism by some turbo krauts
This is an early 1980's book that I figured would have some awesome MP5 spank bank pics and info, but found that it's a mildly awkward translation of a German fluff/propaganda piece on the unit. Still kinda cool, but a big let down overall.
ERTL Force One MP5K
Nope, not a book... it's a metal toy that converts from MP5A2 to MP5SDA2 (and not an MP5K like it's called). I got one when I was a kid in the early 90's, and found another recently on eBay. Not only does it switch from regular to SD, but the mag comes out and it has an old school German starlight scope that looks awkward as fuck on an SMG. Man, times have changed...
Honestly there's only one real negative that I've found with my gun, and that's the changing handle rattles. It came tight, and like your mom on prom night, quickly got a little loose. It just rattles around a bit. And while I know some play is normal on MP5's, mine is a bit worse than any other MP5 I've played with, quite a bit worse. It seems like the changing handle support hole is a bit too big, and replacing that part would require taking off the cocking tube, which is welded on. I actually sent it back to Zenith, who paid shipping both ways and I had it back nice and tight again in a few days. But like before, within a range session or two, it was loose again. Not a huge deal, and I've gotten pretty used to it, but still something I thought I'd mention.
Reportedly Zenith is getting in another shipment next month, so remember:
"Bankruptcy may be on your credit score for 7 years, but the awesomeness of owning an MP5 lasts forever"
Plus chicks dig MP5s, and dicks don't suck themselves. Whatever. Just get one.