Articles Modified or Added in Response to These Questions
RefAR15Buttstocks now includes what might happen if you left out the buffer and spring on a normal semi-auto AR. It also includes a workaround for a stripped out buffer tube screw, as well as the suggestion to just buy a new buffer tube.
saiga 223 rifling twist rate: As of 8/19/08, RAAC has officially and definitively answered this question. The twist rate for the 223 and 7.62x39mm rifles is 1:10, and the twist rate of the 308 is 1:12. This indicates that the Saiga 223 is, for instance, unsuitable to stabilize the heavier 77gr 223 bullets. If a 1:9 AR-15 barrel can't stabilize a 77gr bullet, a 1:10 twist rate won't do it either.
making money reloading bullets: I need to write a bit about what is and isn't illegal in reloading.
short barrel upper receiver "california law": There is no constructive possession in California, but there is constructive possession on a federal level. If you own lower receivers which were registered as rifles, you have a short barrelled rifle via constructive possession unless you happen to own a lower receiver which is registered as a pistol. If you don't own any lower receivers, you're clear as well.
fixing saiga rifle trigger pull: In the 7.62x39mm and 223 versions of the Saiga, it is simply not possible to get a good trigger pull, due to the complicated linkage used to move the trigger back from the hammer assembly. That having been said, some folks have reported significant improvement from meticulously polishing each of the surfaces in the trigger assembly. The 308 (and presumably 30'06) Saigas have better luck, though, due to their one-piece trigger system.
what will happen if the buffer and spring are removed on an ar 15: See RefAR15Buttstocks, recently updated in response to this question.
dillon reloading supplies best price: So far, the cheapest source I've found for Dillon gear has been Grafs's C&R dealer rates.
cugir armory: Cugir is a Romanian factory.
does your semi auto assault weapon have to be stripper clip fed?: California law does not require stripper clips. It does, however, require fixed magazines on semi-automatic, centerfire rifles. Some fixed magazines are frequently fed with stripper clips, however there are plenty of other ways to load fixed magazines.
harlan ak-47 receivers: Harlan is the guy who runs Nodak Spud, which puts out excellent fully-heat-treated receivers.
par3 folding stock: The PAR-3 will take the same folding stocks as the PAR-1 (or any other standard AKM). The forthcoming RefAkFoldingStocks will address this.
ca legal mak-90: No such animal, as the MAK-90 is specifically banned by make and model. You could, however, get a rifle that looks like one yet is CA-compliant, on an off-list receiver.
are conversion kits considered firearms in california?: Depends on the type of conversion. If you mean full-auto conversion, then yes. If you mean something like a pistol->carbine conversion, no, California doesn't have constructive possession so this is legit. However, do not install the conversion in California unless the converted firearm would be California-legal. Just because it's legal pre-conversion doesn't automatically make it legal post-conversion.
where is ps90 made: They're made in Belgium by FN Herstal.
su-16 6.8 spc: This would be pretty neat, but Kel-Tec has not announced any plans to do an SU-16 in 6.8SPC that I've heard of. Theoretically though it should just be a different barrel, new magazine, and an AR-15 bolt head (since the SU-16 basically uses a cut-down AR bolt head, this should be easy).
su-16 silencers: Any threaded-on AR-15-spec silencer should work on the SU-16, assuming you can legally purchase and install it.
can you clean su-16 with 22 cal. brush: Yep, only .001" difference in barrel diameter, which won't make a difference to your brush.
su-16ca legal in ca folding stock: NO, not unless you locked the mag in place. At that point the only advantage the SU-16 would have over an AR-15 would be its light weight. And you'd probably still have to extend it to get it up above 30" overall length, but I'm not sure.
buying a su-16 threaded barrel: Your easiest approach here is to get an SU-16 model with a threaded barrel; it'd probably be cheaper than buying and installing a threaded barrel for the SU-16. If that's impractical, then the next best approach would be to have a gunsmith thread the barrel for you. Trying to replace the barrel on one of these rifles is not exactly a trivial undertaking.
223 caliber in millimeter: The metric designation is 5.56mm, for when you're looking for ammo. However, 5.7mm projectiles are the same as 5.56mm projectiles, so you can see that straightforward unit conversions don't necessarily translate when talking about ammunition.
can you shop ak parts to california: Yep, there's not a single thing illegal about sending parts. However, an assembled full capacity magazine is not a part, it's a magazine. Just like the rifle, you may ship those to CA disassembled all you want.
california magazine parts kit laws gun: A lot of folks are selling mag parts kits to Californians now, and there's nothing illegal on the seller's side about this, as long as the buyer is doing what they're supposed to (only using the parts to lawfully repair existing magazines, or maintain the parts in a disassembled state). It is very advisable however to consistently omit one part from the magazine kit though, because if you sell a parts kit to a Californian who happens to use it to illegally manufacture a new magazine (instead of what they're supposed to be doing, only rebuilding existing magazines), you can be an accessory to their felony. Therefore it is advisable to leave out one part consistently if you're selling a lot of kits, so that they can never say you sold someone all the parts of a magazine which they later illegally assembled instead of using them as repair parts.
russian milled ak parts: These kits haven't been available for a very long time. It would be neat, though.
ak compliance magazine parts: US-made bodies and followers are now available, and there's a site out there I need to link in here which includes instructions on making your own floorplates.
how to tell if a bullet is steel core: Use a decently strong magnet (i.e. not a refrigerator magnet, use something that can pick up ball bearings and such) to see if the bullet sticks to it. If only the nose sticks, then it's steel core. However, if the body sticks then it could be steel cased but not steel core. Steel casings will usually be gray looking. In this case it's advisable to extract the bullet with a pair of pliers or a bullet puller and seeing if the projectile itself will still stick to the magnet. If it doesn't, then the round is steel cased but not steel cored. Some ranges will still disallow your ammunition on the grounds that they can't tell whether it's the case or the bullet, but bringing along the pulled bullet and the case MAY convince some rangemasters to allow it.
anatomy of armor piercing bullets: I need to draw this diagram.
diagram of hollow point bullet: Also need to draw this diagram.
ammunition with steel vs. brass casings: Steel cases can cause more wear on your extractor and chamber, because they're harder than the brass. More significant is that you can't really resize steel casings (some folks who like to live dangerously will reload the steel cases once, but no one I'm aware of is doing it more than once).
carbon buildup from bullets: Actually, carbon buildup comes from burnt gunpowder, not the bullets (which are typically lead or copper).
how can you tell if a bullet is corrosive?: Bullets themselves are never corrosive. However, the gunpowder or primer will frequently include corrosive salts. A good way to test this is to pull a bullet, then set the powder and primer on a sheet of scrubbed-clean steel. The scrubbing is important in order to remove any protective oils which may be on the steel - you need one area scrubbed clean as a test area, and another scrubbed clean as a control. Ignite the powder and primer with a match, then leave the steel for a day or two. If your powder or primer are corrosive, you will see considerably more corrosion on the test area than on the control area. Main reason I recommend a control area is that if you're in a high humidity area, exposed steel rusts pretty quickly so it's important to ensure you aren't getting false positives.
are romanian ak 47 stamped or milled receivers: All of the Romanian AK's I've seen have been stamped receivers. I don't think the Romanians ever built a milled AK, but I could be wrong.
low capacity sten mags: Sten magazines would be very easy to alter into 10-round magazines. While I'm unaware of any vendor directly offering this service, I know that Cold War Shooters does accept custom mag conversion work and they can certainly handle Sten mags.
stanag magazine ak 223: While there are 223 AK's and thus 223 AK magazines, I am unaware of any AK-47 which accepts STANAG magazines. It should be theoretically possible, however.