I have owned my SKS for 17 years. It is a great all-around gun. I have killed several deer and used it lately to slay some pigs.
The gun has the rear sight with the elevation adjustment. Not being military, I'm not really sure what all the numbers mean. I have the adjustment set all the way back on the number 3 (?). The rest of the sight is then graduated starting at 1 then up to 10 (I think) I realize the closer you move the adjustment to 10 the further out it is sighted. My question is, "Do I leave the sight adjustment set on 3 (the furthest back) for general shooting? I don't shoot it much further than 50 to 75 yards. I have a scoped .270 for further out.
Second question. Is there a better aftermarket sight for this gun? The rear sight really sucks.
Thanks for the help guys.

I had one that I put a Mojo brand rear peep sight on. I also took the front sight post off, chucked it up into a drill and spun it against a fine file to thin it down to about 1/2 the original width. Then I hit it with emory paper and re-blued it.

These two things, along with a do it yourself trigger job, made a huge difference for me; the stock sights would not get a good sight picture for hitting the 100 yard targets I was using. Instead of being happy with hitting just a pie plate even while using a rest, I could get something that resembled a group.

As far as the origina sight goes, the graduations are in meters. 300 is the "battle zero" setting

What he said.

The US Army uses a 25m/300m zero for 5.56mm, because at 25m you're dead on, at 300, you're dead on, and in between you'll vertically vary no more than an inch or two either way, and a hit in the crotch is about as good as a hit in the chest honestly.

Not sure what the old Soviet here-to-here settings were beyond 300m, but most of the old Mausers (8mm) were 50/200 so it should be something close to that.

Tech-Sights is an excellent add-on which will give you an M16 type rear sight and a longer sight radius.