Tuning the gas system does a number of things for you but imo the biggest gain you will see is reduced recoil and less movement through the optic, two of my ARs have carbine gas systems and I saw the biggest benefit on those rifles, my PSA was WAY over gassed and it would throw brass all the way across the shooting bays, the buffer had a ring in the face of it from the amount of force the bolt was hitting it, it was so over gassed the gun was not extracting properly, I was having to replace buffer springs about every 2-3k through the rifle just to get it to run properly, My BCM had an adjustable gas block on it from day one and it always left a nice pile of brass about 3 o'clock and the rifle shoots extremely flat, once I put the SLR adjustable block in my PSA is shoots about as well as my BCM does.
When I built my wifes AR I went mid length and did not go with an adjustable gas block right away, I put 100 or so rounds through the rifle and it shot pretty flat, the ejection was good to go but my wife mentioned that my BCM and PSA didn't seem to move around as much when she shot them, so I put an SLR on her rifle and it shoots just as well if not better than my carbines, with a mid or rifle length gas system I don't think it is nearly as noticeable but imo it is noticeable enough to warrant the $100 bucks if you are wanting to get your rifle to shoot as flat as it can.
I don't know if this is the "proper" thing to do, but I normally tune the gas system shooting the value box .223, then run a few rounds of wolf/tula all the way through the hotter ammo to make sure the rifle feeds, chambers, ejects and holds the bolt open in the last round as it should.
I am in Greensboro and if we can work out a time and place you are welcomed to shoot what I have, if you have an AR with a non adjustable gas block to shoot and then shoot mine you'll notice a difference,
