I understand the tight group mentality....I suffer from the diseased mind myself. Before getting antsy about the 1" group and starting to change loads around, make sure you have no contact points along the barrel channel with the barrel. Make sure action screws are adequately tightened. Be sure the rifle is sitting on the sandbags at the same location on stock from shot to shot. I have gone as far as removing swivel studs from forend as they come into play, albeit minimal, during recoil. Once the rifle is ruled out, then its time to attack the load.
For the absolute best accuracy with any given caliber / load I have used the following:
Load 20 rounds in .1 grain increments.....example 38.1, 38.2, 38.3....etc (keep in mind you max load capacity. I have gotten down to 12 loaded rounds instead of 20 that go up and down .6gr total from any decent MOA handload. Keep all OAL's, Trims, Primer, etc standard for all. Record each shot taken for bullet impact. Keep an eye on how the group opens and closes. You will see there are "sweet" area of tiny clusters in a .3-.6 increment range of the shot string. This will give you the best starting point to fine tune seating depth from. Once all rounds are fired, pick the tightest cluster and a central increment grain for the group then you are set.
This seems like some work, and it is, but in the long run, it is very rewarding and informational to see exactly how tiny variances of powder make changes in the projectile strike point.
I do a quick clean between shots and walk to the target board to record and allow barrel to cool a bit. This method also gives you a good excuse to practice repetitive shooting technique, trigger control, breathing, etc. which will also tighten your groups up in the long haul. There isn't a rifle in my collection that doesn't shoot 100yd cloverleafs or better.
For those who think I'm crazy, I wont 100% disagree, but once you try the method, you will see how much time you actually save from making "estimated guesses" on how deep to seat, which primer, etc.
Feel free to PM me if you have questions. You can contact me by email email@example.com
as well. Good Luck....I'd wager you end up thinking you missed the paper completely when you fire a round and can't see it on paper, as it went into the prior hole.