Ultimately, it's the goal of TGW to know everything. But until then, the best way for it to grow in usefulness is for articles to get written in response to searches you folks make.
Articles Written or Updated in response to these questions
I do tend to give quick responses to a lot of the questions in here. However, some questions come up often enough (or the area is murky enough) that they warrant new articles or updates to existing ones.
ar-15 fixed magazine: As codified in law, a fixed magazine rifle is any rifle in which a magazine cannot be detached from the rifle without the use of a tool. There are a number of commercially available kits which convert an AR-15 into a fixed magazine rifle.
legal california assault rifles: As noted here, assault rifles per se are restricted to a very small set of individuals. An average citizen may not buy or possess an assault rifle, but may possess rifles which do not qualify as assault rifles under California law.
monsterman grip legal in california: The MMG has been neither approved not disapproved by the DOJ. However, various DOJ phone clerks have recommended it to callers.
ca legal pistol grip for ar-15: There is no "California-legal AR-15 pistol grip". There are, however, grips which attach to the pistol grip mounting stud and do not provide a pistol grip. One important note is that pistol grips are only illegal on semi-automatic, centerfire rifles with detachable magazines. 22LR, bolt-action, or fixed-magazine AR's may legally have pistol grips.
rifle stock retaining bracket ar-15: You are probably asking about the SRB, which is actually a Spring Retaining Bracket. This device is almost never used in new builds, as it has been superseded by the Monsterman Grip. Mud of Calguns, the SRB's designer, has moved on to work on the http://blackstararms.com/ Blackstar Arms AR-15 variant lower receiver.
.22 california legal ak47s: Any federally legal AK-47 which is not on California's specific ban list, is California-legal. That having been said, the Armscor AK-22 is frequently thought of as an AK, and it is not even remotely related to the AK-47. However, the Romanian military trainer, presently marketed by Century Arms, is indeed a modified AK-47, and I can personally state that it functions quite reliably with the right brands of ammunition.
legality of gun ak parts kits california: Completely legal, on a state level. However, bear in mind that constructive possession can apply to kits with barrels under 16". This is a federal issue, not California.
ps90 barrel replacement california: At present, the only commercially available replacement barrels for the PS90 are the 10" SBR barrels available from CMMG. A 10" barrel would only be useful with a permanently affixed non-flash-hider extension. I believe a 22" barrel would actually be ideal for California purposes - no "evil features", and it would also bring the rifle's overall length up to 30" without the use of additional stock or barrel extensions.
ptr-91 magazine lock: There are two PTR-91 magazine lock designs currently being used in California. One is a "bullet button" style, designed by Radd of Calguns.net and sold by Cold War Shooters, and the other was designed and manufactured by Rorschach of Calguns.
buy ar15 from another state and move to ca: That's legal, as long as the AR-15 is not on the banned list and complies with the SB-23 feature list.
california legal short barrel rifle: California does not sign off on SBR permits for modern weapons, generally speaking, unless you've got lots of political connections or are making movies. However, California doesn't get a say in whether or not you may cut down a curio and relic weapon. So, you can make all the SBR'ed Mosin-Nagants, etc, you want in California. Update: In late 2009, to all intents and purposes ATF stopped signing off on NFA alteration of C&R weapons for Californians.
pistol grips for sks assault rifles: An SKS assault rifle is any SKS rifle with a detachable magazine. This means the Russian and Chinese SKSes; however, the Romanian, Yugoslavian, Albanian, etc "SKSes" are not actually SKS rifles and may legally have detachable magazines. You may not have a pistol grip on a detachable-magazine SKS. However, a pistol gripped stock is completely legal on a fixed-magazine SKS.
how to sell california assault rifles: You may sell a registered assault rifle, however it may only be to an out-of-state party (no Californian may buy it), and the transfer must be done through a California dealer with an assault weapon dealer's permit. See LegalCaliforniaDisposalOfAssaultWeapons.
is collapsible stock for an sks legal in california: Yes, provided that you don't have a detachable magazine on the SKS.
is it legal to do a private party transfer not face to face: Apparently not. I thought you could, but was informed otherwise.
ammobros: They're an ammunition store with branches in Cerritos and Ontario, and sell a few guns too.
is it legal to have a threaded 22lr barrel in ca: On a rifle, yes. Threaded barrels are not regulated under California law on rifles. They are, however, strictly prohibited on pistols.
is it legal to remove a thumbhole stock: Sure. Whether it's legal to install can be questionable, but removal is never regulated.
ca approved ar15: California (specifically, Ignatius Chinn) has approved the Evans Gunsmithing welded-magwell AR-15. Letters of approval exist for most of the various brands of off-list AR-15 receiver as well.
ca approved garand: Unaltered M1 Garands (i.e. those which still use en bloc clips) are all California-legal. If they've been modified to accept detachable magazines, make sure you don't have a flash hider on the front.
fal monster man grip: He keeps talking about doing one - there is none yet.
General AK Questions
.22 california legal ak47s: What you want is the WASR-22, from Century Arms.
nhm 90 illegal: As far as I can tell, there never was an NHM-90. There's the MAK-90 by Norinco, and the NHM-91. The NHM-91 is, like the modern AES-10B, a sporterized RPK with a 20" or so barrel. The MAK-90 is an AK-47 variant with a thickened receiver and a thumbhole stock. In California, the MAK-90 is listed and definitely illegal to bring into the state, however continued possession of a properly registered MAK-90 is legal. Federally, there's no law against owning a MAK-90 or NHM-91.
General AR Questions
50 beowulf conversion kit: All you need is a 50 Beowulf upper and magazine. The magazine isn't 100% mandatory, but it does feed more reliably than an unmodified one.