It's cheaty, but if you're desperate, you can also go back to the Swamps and travel to the Cordon through the northern level changer, which will have become activated when you first traveled there from the south.
I'd only call it cheaty from a gameplay perspective, but from a roleplay perspective it makes perfect sense to take the easiest path. Makes me wonder why the Clear Sky guide sent Scar towards the army outpost in the first place, as if Clear Sky wanted him killed...
---QUOTATION--- When you get to the Cordon, you'll need to jump over the barbed wire fence by the railroad tracks where it is lowest if you want to avoid invoking the wrath of the stalkers guarding the checkpoints - assuming you're playing vanilla. ---END QUOTATION---
The easiest way is to simply use the guide in the Stalker base. But I recall I've walked past the stalker guards too (I've always played vanilla CS), they complained a little but didn't shoot.
You CANNOT kill the gunner behind the RP-74 ( PKM ) because there is
NO gunner operating it. There is usually an NPC standing near it but he
has his own weapon and does not operate the larger gun. I know this
because I have actually come up behind it ( No Mods ) and seen this.
I've also wiped out every soldier on that base and had the gun go silent.
Then I have stood directly in front of it without harm. Only when the
Military respawns appeared way behind the PKM down the road ( far
from the weapon ) would it magically come to life and fire unmanned.
Now getting back to the issue at hand. What helps the most is your
preparation before departure. Are you leaving the Marshes in haste
poorly equipped or did you take full advantage of all there is and you
have the best armor in the game? If you enter the Cordon poorly
equipped ( please don't use the cheat by utilizing the other path )
you will be damaged or killed easily. Get the right equipment and
plan the time when you go, the path you take and how you move
and you can get the lightest damage at worst in your endeavor.
First, you should be leaving the Marshes with all of this including the
artifacts and it does include the CS-1 Armor with a BP rating of 60: http://i.imgur.com/tS1h5fH.jpg
Second, choose the time you go. I think the best is at night when the
visibility is the worst for the Military and their soldiers have more trouble
finding you. Once you enter the Cordon wait at the top of the hill and
observe the situation ( using your night vision ) of which you are safe
behind the tree. Go forward quickly descending the hill as the PKM fires
and you want to reach the bottom where there is a large boulder. Wait
there until the PKM empties it's magazine. Once it goes silent and is in
the act of reloading, move quickly again going to the downed tree and
to the left directly to the Rookie Village up the hill. You should need
nothing more than a bandage/medkit at the worst using this method.
It's cheaty, but if you're desperate, you can also go back to the Swamps and travel to the Cordon through the northern level changer, which will have become activated when you first traveled there from the south. When you get to the Cordon, you'll need to jump over the barbed wire fence by the railroad tracks where it is lowest if you want to avoid invoking the wrath of the stalkers guarding the checkpoints - assuming you're playing vanilla. If you're using the community patch, you'll be able to pass the checkpoints without harassment when approaching them from the north, so long as you came from the Swamps.
Make sure don't reach your backpack to max. weight limit. Actually when you stand behind the big rock you can sprint directly to the road. But you need lots of medkits (about 10-15) If you have enough medkits like i said you can cross the other the side of the road directly. Don't turn left or right when you sprinted. And during the sprint, prepare your fingers to use medkits against the machine gun hits. Usually machine gun don't hurt if you sprint directly to somewhere