Also would the SW5k receiver be register-able, it says that its not been welded yet?
No. These receivers aren't either. You can read the law as it applies January 1, 2017 here:
To register according to a plain English reading of the laws, before January 1st, 2017 you must possess a semiautomatic center fire rifle which "does not have a fixed magazine," and has one of an enumerated set of features including a pistol grip and flash hider. It cannot have a detachable magazine and feature because that would make it an illegal unregistered assault weapon under current law and not legally possessed to be grandfathered under the new law. A "bullet button" makes both magazine definitions work. One can be installed on a paddle release gun when you omit the corresponding magazine release contact piece for easy reversion to original HK ergonomics once you have a Registered Assault Weapon, flee to a free state, or merely vacation elsewhere.
The same magazine restrictions apply to semiautomatic center fire pistols with a different set of features, where the fore-end and threaded barrel are relevant. Pistols must also begin life as single-shot bolt or break-action firearms, where you cannot start with a raw receiver because those can only be DROS'd as long arms and would become illegal short barreled rifles under California law when built as pistols. As of January 1, 2015 temporarily altered semi-automatics are not allowed. DOJ sent a letter to FFLs asserting Franklin Armory's never-fired AR15 pistol with a wooden dowel in the buffer tube was temporarily altered although as the manufacturer they guaranteed it had never operated semi-automatically. DOJ knows what guns you have, and could ask you to surrender them when it changed its mind. People mill 80% AR15s and bend flats to steer clear of these issues. Searching calguns.net for "SSE 2.0" will yield other peoples' opinions.
Without parts like bolt and carrier a gun is not semi-automatic although that's less legally certain on a HK clone receiver than an AR15 lower with bolt action upper halves commercially available. Without barrel a receiver isn't center fire - you could press in a .22 rim fire barrel. Without a stock it's not a rifle - you could build it with a pistol grip or spade grips, although a paranoid person would avoid dropping under 26" total length so it's unambiguously not an illegal short barreled rifle. You may also be short a banned feature.
There's a lot of discussion on calguns.net surrounding SB-880/AB-1135.
The laws say it must be in that configuration between January 1, 2001 and December 31 2016; but do not specify it needs to be that way on Midnight, January 1 2017. In theory parts like bolt carrier group, lower, and butt stock could be in your possession only long enough to mate with the receiver producing a currently legal gun which becomes an Assault Weapon on January 1, 2017.
I feel your pain.
Gunmageddon moved the timing on some of my planned purchases from "someday" to "this year before a potential post-election panic" and shopping has been less than relaxing.
I bought a December, 2000 Special Weapons SW5 HK94A2 clone to guarantee I'd have something, and am considering my options trading up to something nicer with a proper cocking tube and hanger. Atlantic's $1500 Omega complete upper would be nice if it was in stock, BPP's $1300 group buy sans bolt carrier group / rear sight is close (no paddle release, costs more once you add a bolt carrier group and sight), and I wonder if I could get a barrel pressed in and triple tower installed on a receiver with all welding done soon enough.
sorry again for the newb questions, im accustom to ar's but have always loved hk firearms. As far as building one myself as interesting as it would be i know that i don't have the skill set to do so, just gotta wait till a later date to build.
Legally that's not an option after January 1, 2017 without going "featureless" on a rifle with a grip wrap (Solar Tactical makes them for metal lowers and at least some plastic ones) or fixed magazine on a pistol, loading through the ejection port.
Our software jobs and weather are nice in California, but the gun laws stink.