chicken or the egg?

[rangeball]

Age old question with a twist. When ffing a bullet, how do you tell when sizing or powder charge is what should be adjusted for best accuracy?

Say you use a medium load pressure fit and get 1.5 moa grouping. What tells when sizing is perfect and you should shift your focus to load volume?

[Deleted]

It's both.
All of my barrels are a little different.
Some barrels like the bullets tight, others loose.
Changing from H4198 to IMR3031, I have to loosen the die up 1 to 1 1/2 notches on the Swing Lock FF die. IMR3031 is a dirtier powder.
H4895 has been the cleanest powder for me and I have to tighten up the die about 1 notch when I change from H4198 to H4895.
Some of my barrels shoot a little better with wads.

Try going to a know accurate powder load wt. ie. 70 grains H4198, and start dialing in the die.
After you get your most accurate groups at a certain FF die setting, try adjusting powder wts.
It takes a little while, but after enough shooting, you can watch the groups open up or tighten by moving the FF die setting.
You can do the same with powder weights.
I really got used to shooting super tight bullets in the 416, when I wasn't using a booster.
Now I'm setting myself up to change from boosted loads to loads I'm shooting with a larger vent orifice or double barrel vents.
Then I'll try the 209's vs. LRM's with the larger vents.
The variables are endless.
But I know I can always fall back on a 310 APB with 70 grains of H4198 in my .458's. That load just plain shoots well for me.
In my 416's, it's a stout dose of H4350 and a 325 MH that shoots very well.

Good Luck!