Very nice buy. It's not often you get to cherry pick from more than one, let alone a "lot." I'm not a big fan of the trough sights, but I'd definitely take one at that price.
There are a lot of subtle differences between models. Full lug, half lug. Fixed sight, adjustable sight. Heavy stainless frame to super light scandium frame. 6, 7, 8 shot, etc, etc. The Smith & Wesson site is as good as any for giving an overview of the sizes, weights, etc. I think the best...
If your FF3 ever breaks, they will fix it or replace it. Even if you accidentally drop the gun on concrete and break the sight, they will take care of you. I had mine on my .45 Range Officer for 5,000 rounds and one day noticed a series of cracks at the bottom of the glass. No idea how it...
No bans on ownership, but it can't be sold from one state to another. It can be sold within your state only, and even then you need reasonable proof that it was imported pre-ban. There are some fairly complicated exceptions.
No, same diameter. But look down the chambers of your revolver. You'll see that they're not straight all the way down. They neck down very slightly toward the front. The longer .357 cases won't fit past that slight bottleneck in a .38 spl.
The overall length might be the same, but the case is a larger diameter than the bullet. A .357 case won't fit past the throats in a .38 spl, regardless of how short the whole cartridge is. If the chambers were the same diameter from back to front, you could load it and close the cylinder, but...
You don't have to set anything to see a dot, other than the power level setting. If you're looking at it straight, you'll see a dot. If you can't see a dot with any alignment, there's something wrong.
My Matchdot2 sits atop my 629-6. Only a few hundred rounds so far but it's held zero. It already survived 20,000 rounds of 22LR, but that's probably not too remarkable.
You won't find many for $50. You'll have to sight it in, but it's pretty easy. Just turn the arrows toward the way you want the shot to move. Start at 5 or 7 yards so you can get the first shots on paper.
Where is your seller? If he's in the U.S., he needs an export license to ship gun parts over $100, and a sight is considered gun parts. You said it was cheap. Under $100?
It looks like you're seeing the glow from the dot on the inside, but you can't really see the dot. Maybe ask him to send a better pic that shows a clear dot.
Although a person has to take Wikipedia with a grain of salt, it usually has a good overview of S&W models. This page goes into some detail on the variations and dashes:
Smith & Wesson Model 686 - Wikipedia
I don't know, now I'm as lost as you are. 22771 LOOKS like it would fit all the newer ones with the pin-on. I have no clue how the 22770 attaches to the gun. I'm sure someone who has dealt with these will be along. I'm just going by what's on their site.