I am more interested in a low Extreme Spread (ES) than a single digit SD.
The reason is due to impacts at longer ranges, if velocity is swinging that much, it makes hits at those ranges more difficult.
Also, ALWAYS go by what the target is telling you, there's no point getting low ES/SD numbers and the bullets are spraying all over the target. Getting low numbers does make the load a shooter.
I have a load in a particular rifle that at 100 is pretty much BR groups, 10 shots in the same the same hole...yet the ES is 100fps. The bullets just exit in the oscillation at a point where it is still at either end of the velocity range, it's a fluke that is rare to be sure.
Your example above of a ES of 30 is about as good as an untuned load gets in a standard rifle. Tweaking seating depth and/or charge may bring it down to the teens, but only change one or the other.
So your looking for e s under 20 .I'm new to reloading would you play with seating depth or charge to start with .I'm 125 fps then what the book said I should be and I'm .1. Grains under the max where would you start?