Here's the process I use that's proven to work very well on everything from .17's to the .30's. Broken down, it's this way in order of importance:
Step 1: Tune with the powder charge starting from the bottom and going up.
Step 2: Seating depth after powder charge tune is established.
Step 3: Final tune with neck tension
-With a stripped bolt, adjust the seating stem until the rifling marks just disappear on the bullet.
-Measure and
record the seating stem length as the 'touch point' for
that particular bullet.
-Make the seating stem .030 shorter than the 'touch point'. This establishes a solid jam/seat.
-Use a neck bushing .004 smaller than what the neck measures with a bullet seated.
-With a lower end charge wt., go up in .3-.5 gr. increments (depending on case size).
-
Using wind flags and the same POA, shoot 3 shot groups at each weight until you get pressure.
-Select the best 3 shot group and shoot another one to make sure it repeats.
-With that load, shoot 3 shot groups, bumping the seating depth back .003-.005 at a time.
-With the seating depth that shoots smallest, shoot it again to verify it repeats. Record that stem length.
-Now back up the neck tension .001 at a time and pick the best group.
-Shoot a 5 shot group with that load. It should be about 40% larger than your identical 3 shot group.
If everything looks good at that point, I'll load 10-12 and shoot a group to see how stable it is.
As you go along, you'll get a sense of what the barrel likes pretty quickly. From 30-40 rounds is all it normally takes to get a sense of things. But I'm more of a plodder than most and do a fair amount of A-B-A testing, too. Most BR level guns will show good accuracy at multiple charge weights. On a 30BR for example, from the lowest charge until you can't get any more in the case, you'll generally see three good accuracy levels. If the tuneup is good and flat from 34.2 to 34.8 for example, plunk it down at 34.5 and go from there. Nothing good comes from living on the edge...whether that edge is high or low.
If you choose to live on the razors edge, you're gonna' bleed a little.
One thing I do with a load is test it when the winds at our range are from either 3 or 9 o'clock. With a 3 or 9 o'clock flag position and a dead center hold, virtually all of the wind induced vertical is eliminated and what you see 'on target' is how stable the load is across the full value of the wind. Now, not everyone agrees with this concept. And it can certainly be dependent on the features of the range, too. But it makes sense in my brain.
The target below shot this last May shows this pretty well. The top two groups are hitting the flags as best I could for direction and speed. The bottom two were fired purposely ignoring the wind speed and just concentrating on the flags position. POA on all groups was the center dot. On the lower left group (6 shots in the push), I gave the scope a couple clicks down before firing it. The wind speed was slacking off (wind was from 3 o'clock) and I didn't want to risk shooting out my aiming point.
I do send a few across the chrono just so I know.
In SRBR, accuracy and a solid stable tune up are everything to me. OCW, ladders, ES, SD, OBT, etc. mean a little bit less than zilch.
Just how I approach it..... -Al
