When I "work up a load," I do this:
First, I load 10 rounds of each weight of each powder I want to try I load the cartridges started at the bullet manufacturer's minimum recommended load for that bullet and load up to max recommendation, half a grain at a time until I have cartridges close to or at the max.
Second, I bring "backer paper" and plenty of targets to the range. I shoot each ten round group with a fresh target and fresh backer paper to insure I only have a ten round group on that paper and target. I don't adjust the sights or the rifle in any way, so as to not affect the groups. I measure the groups outside edge to outside edge, to be as conservative as possible. I record each load on the target and in a "dope book" for reloading as well. Then I keep the targets until I get home and record the data. That way, I make sure I get the data on each load.
Once I find a load that is "close" to what I am looking for, I attempt to fine tune that load using smaller increments of powder above and below the best group I had for that powder/bullet. I take the new loads and repeat the process, seeing if I get an even better group.
I then stuff all the data for the loads into an excel spreadsheet and see what jumps out at me. If the velocity and accuracy is good for the range I'm wanting to shoot in, I'm done and I load up a batch of however large a quantity I want for that rifle. If it's a hunting rifle, enough for a couple years hunting. For target rifles, anywhere from 200 to a 1000, depending on forseen usage.
I may try up to three or four powders if I'm not satisfied with the results of a single powder.
All that said, when it comes to bolt action rifles, I make sure the barrel is free floated (able to slide a dollar bill around barrel from action to front of stock or vice versa) and the rifle has had a trigger job at a minimum. Add a 10 degree target crown and steel bed the action if it appears to be worth while.
To date, most rifles I've worked with are 1.5" and below using the above procedures. It is a bit of work, but it's been worth it. Newer, more modern bolt actions are fairly easy to get down around an inch and below using this procedure.
Regards,
Dave