- What is the visual difference between a chrome/normal barrel? Chrome is shinier?
You mostly have to go by make/model (i.e., all the Romanian civvie AK's are chrome lined, AFAIK); research what models are and aren't before you go to the show.
However, the chrome lining on my SAR-1 extends out of the barrel a little onto the muzzle crown, and looks like satin silver paint (not high-gloss) in contrast to the surrounding finish.
- What features on the receiver to look for (i.e. I see all kind of talk about "dimples" and other things).
That depends on the model. The receiver is wider than the magazine, so there has to be something in the magwell to narrow that space so the magazine doesn't flop around. SAR's have stamped oval dimples above the mag opening; WASR's have riveted blocks instead.
You can see the magwell dimples on my SAR-1 pretty well in this photo:
The dimple everyone is talking about is the oval indentation just above the magazine, behind that big rivet.
- Are canted sights obvious? Will they be obviously tilted? Left/right, or fore/aft?
Left/right is the problem (occurs when whoever assembled the rifle from parts didn't take the time to line everything up straight). If the cant is bad enough to worry about, it will be obvious.
What you want to do is shoulder the rifle a little low (or look at it from the rear) and see if the front sight assembly is leaning left or right compared to the gas block (the slanted metal part above the barrel, in front of the upper handguard). The gas block may also be misaligned, so check both to ensure they're on straight.
-Can all receivers accept a folding stock later?
As far as I know, yes. HOWEVER, you may be limited to a certain type of stock. SAR's and WASR's can take Romanian and East German sidefolders, as well as aftermarket folders from Ace and Tapco. Some other makes/models may require different stocks (the Polish underfolders come to mind). Vepr's are built on an RPK-style receiver and don't accept AK-style stocks.
- If you want a scope later on, the mounting rail is on the left side, correct?
Yes. Left side, sort of above the trigger guard area. It should be attached to the receiver by two rivets, one at the front and one at the back. Sorry I don't have any pictures handy.
Some other helpful info:
The lever on the right side, just above the trigger, is the safety. All the way up is safe, all the way down is fire. The magazine catch is a little lever on the gun's underside, at the front of the trigger guard/rear of the magazine well.
With the safety on, you can pull the bolt back just far enough to see that the chamber is empty. However, to pull the bolt all the way back, the safety has to be off (safety feature to keep you from accidentally chambering a round, I suppose). I'd ask the seller before working the bolt, though.
The button at the rear of the receiver cover is the disassembly button. You push that button in all the way, and the receiver cover comes off, along with the recoil spring guide and recoil spring. Field stripping instructions are all over the 'net. I don't think it's necessary to field strip one before buying, though (I didn't).