Front tension set screw,
you never set it after you had adjustment screw set, to hold the adjuster screw to it setting if the set screw walked out on its own.


So, we start with a single round in the mag, it charged into the chamber and the empty mag still in the mag well.

The front tension set screw is backed out a few turns to allow the adjuster screw to move freely.

Now with the adjuster screw turned all the way in with light tension as it seats home, we start out with a half a turn out, rife the round and see if the bolt locks back on the bolt catch.  If the bolt does not lock back, adjuster screw it turned out more, and we single charge and fire the round again (empty mag in the well).

Once you get the bolt to just lock back on the bolt catch via the single mag loaded round with the adjuster screw set, turn the adjuster screw out 1/4 turn more, then re-tighten the front tension screw to lock the adjuster screw in place.

And the tension screw is the screw on the front of the block and adjuster screw is the screw on the side of the block.


As for the distance that the adjustment screw needs to be adjusted outwards, it different for every rifle.  If the barrel gas port is correctly sized, or you have a slight leak in the gas system, then the set screw may have to be set with the block gas port passage wide open/ adjustable gas screw way out.  

Hence where the adjustable gas ports come in handy, is when you are shooting say 69gr ammo, since it use a slower burning powder, which increases the gas port pressure to the barrel gas port isntead.  Same goes for running a suppressor, since this always increase the back pressure of the barrel, which increases the gas pressure to the barrel gas port to cause over function as well (bolt unlocking too soon).  

As for 55 or 62 gr ammo and the gas port correctly sized for it, then the adjustable gas block is a waste, since no gas reduction to the carrier is required to have the rifle cycle correctly instead.

Lost on why you can not get to the tension screw.

Its on the front of the gas block and even with it deep within a longer float tube type hand guards, should still be able to get to the set screw with a long handled T allen wrench to tighten it that way instead.

But yes, having to adjust the set screw out as far as you have, is normal.
Hence you are not shooting ammo that may over charge the gas port system (say Mk262)to required that the gas passage be adjusted down, so with the ammo being run, the gas passage needs to be run wide open instead.

Wiha  has these on the cheap, and should be long enough to reach the tension screw,
http://www.all-spec.com/Catalog/Hand-Power-Tools/Screwdrivers-Accessories/Screwdrivers/26416-56114?gclid=CLKNqZyD-s4CFQiQaQodQWoHMw

If you want to go cheaper, the Tora instead,

https://www.zoro.com/eklind-hex-key-tip-size-116-in-pk10-15104/i/G1017782/?gclid=CN2WoseD-s4CFQ0DaQodrdoAvg&gclsrc=aw.ds

Or if push comes to shove, then just a 1/16" bit, and use a long magnetic Apex holder with on a screw driver type handle if you need more extension isntead.
http://www.hobbylinc.com/htm/int/intc22809.htm


Hence if you are not using the tension screw, then once you get the adjustment screw set correctly for the load your using, you going to have to stop shooting until the locker agent sets up instead (and play the same game again if you change the load)..

There you go, and with it in your range bag, making setting adjustments will be a snap/don't have to wait for any type of thread locker to set up instead.