G'Day knackers,
for a factory rifle, I'd do the following case prep.
*flash hole deburr
*Uniform primer pockets (and clean pockets with uniformer when reloading)
* maintain the case length to within 0.005" (trim to shortest case length in batch) & deburr.
I dont weigh any case I use in competition. I have proven it to myself that it is a waste of time. Nor do I worry about case wall run out or even check loaded rounds for run out. Quality sizing & seating dies with quality brass should take care of that (assuming the chamber is cut true..........!)
Most important items are listed above: ignition and consistent bullet/neck tension.............which controls bullet "grip" and "release"
Bushing dies can adjust neck tension very easily if you have them, some loads like more; some like less bullet "grip".
If you have an ideal world, a tight neck chamber and neck turned cases helps a lot with
much more even and consistent bullet "grip" or "release". That is the amount of force required to pull that bullet out of the case. If more work has to be done to move a bullet from any loaded round compared to the next, it means it changes the pressure curve and harmonics of the gun.
This is what I call "bad"
I believe if you can get the pressure vs time curve more consistent from shot to shot you will more likely to develope pin point accuracy due to the vibrations through the rifle being more consistent. The eveness of the grip/release of a bullet by the case is very important, much, much, more than the weight of a case ever will be.
So very even bullet grip and bullet release forces are what I call "good"
In a factory rifle where close tolerances are not the norm, so it it much harder to achieve consistient harmonics, but in an accurised/custom set up it seems to be the case.
As for setting bullet length.............
* I size a case, seat a bullet long so I push the bullet further into the case as the bolt closes
* remove and measure case oal with a bullet comparator and record length.
* Use a kinetic bullet puller to make the oal longer than seater setting, no need to remove it completely
* Re-seat it again, chamber, remove and measure again.
* repeat until you get consistent dimensions.
You will be surprised just how consistent you can get, I usually can get readings to be within 1 thou or so. It doesnt need to be that accurate, it is simply a starting point to compare all further seating depth settings for that bullet.
This is called the bullet jam figure, usable only by you with that rifle and barrel/bullet combo. New bullet; redo the measurements. Every fired 300+ rounds or so (as the throat erodes) check setting again, this will also give you a rough estimation of the throat wear over time too.
The beauty of this method is the grip lessens everytime you move the bullet until it has a nice "grip" that allows easy seating and easy push back for any bullet into the case.
By increasing the oal from the bullet jam figure, the longer case/bullet combo will help to align the bullet with the bore). Shortening it by around 0.015" means you are probably just off the rifling for a hunting load. I usually load all my comp loads to
jam figure + 10 thou inch and know it is usually me missing a condition rather than the load not working. This probably gives around >95% of the accuracy the rifle is capable of. Miss reading the wind can more than double the size of the group or rifles grouping ability (aggregate group size)
The main point to remember is that shooter who always practices/competes always seems to place well or win............why? Because he knows his rifle/load, can read the wind, and has his shooting technique down pat.
Hope this helps, if not keep on asking!
Cheerio ned
