+1 to the above (barreled action part mainly)
They (Black Market Parts) also do/did sell stripped barreled actions on gunbroker, but as to whether those were rejects or leftovers from the assembly line is anyone's guess.
My "SW5" branded clone had cycling issues right out of the box. I picked it up second-hand (from gunbroker I think) for $1100 in 2005. At that time there was less market saturation, and it seems to me a higher % of users were having trouble with NIB Bailey clones than in later years.
Anyway, my gun was his "newer generation" (at the time) receiver, which is stamped sheet metal (like HK), as opposed to the earlier cast receivers. So mine accepts A3 stocks for sure (most cast ones didn't) and has a HK-profile correct-looking cocking tube and fore end hanger. (And I was checking every seller's photo for those features too. The earlier ones could look really gaudy.)
The problem I had was FTE (ejection). Sometimes the brass would fall down into the trigger pack.
I initially tried a HK extractor spring, but that only reduced the instances of the FTE. Then a carefully-inspected (for bottom-of-bolt-head clearance) HK 9mm ejector failed to solve the problem, so I got a complete used HK action 3 bolt group (I think for $250). Upon comparison, I could instantly see how crappy the SW version was. As was mentioned in the preceding post, no tungsten in the SW.
That seemed to completely solve my FTE. I wasn't done though. Like boricua9mm, I didn't like the factory trigger group and housing (although mine was a welded steel SW repro box in a steel housing), so I bought a $90 G3 polymer SEF which I converted and installed. I fit it precisely (with my Dremel
) onto the semi-auto receiver shelf, so there was no movement. It felt like a new weapon. It's run 100% ever since.
Mine works with any mags, although I avoided whichever mags they said to avoid on here (early Korean unmarked?) and got 6-8 Korean ATI-marked mags that have all been 100%. The SW mag included with it has also been 100%. I have 6 genuine HK mags also (100%) and a Beta C 100rd mag (100%). I did take all my Koreans (with their rough parkerized finish) and drench-scrub them using oil and 0000 steel wool inside and out, (then dried). They became much smoother and nicer-looking (dark black like HK) so I don't know if that helped them any. I saw that tip here.
The mags have some wobble fore-aft in the mag well. I played with a genuine HK, and it was not as sloppy. I will try to TIG weld before a refinish to tighten that.
The Beta C did not want to insert the first few times due to interference on the front side of the mag well. The plastic gave way and it's fine now.
I also replaced my plastic cocking tube support with steel, just due to preference. That also made it feel more "real" and solid.
Mine has a 3-lug barrel, but I've only put a HK flash suppressor on it. That has slight rotational play, which I think is normal even on HK barrels. I have heard the lugs can be out-of-spec. I'm hoping to get an AAC (or JB Tac) TiRant 45 3-lug adapter, but haven't tried a can on it yet. My barrel is not threaded. If a can is wobbly, I'll thread it (either at just the tip
, or get a 3-lug to replace mine, threading back to the triple-frame). Probably the 3-lug replacement, as I like QD cans.
I also want to add a paddle mag release, which I think all the BW5's included.
My rear sight isn't dead-centered, but it's not maxed-out either. My stainless SW barrel shoots great.
Mine was run with a select-fire pack a lot (or way more than semi) and has been 100% (since upgrades per above) with no problems.
Here is my buddy SouthernSoldier dumping the Beta.All-in-all way more problematic than my MKE AT94 K clone, but it was my first MP5 and has been 100% for a long time now, so I love it. It's an attention-getter at the range, and a real crowd-pleaser with the pack installed. The ladies enjoy shooting it due to low recoil + fun = WIN.
So congrats, OP. Enjoy!