You can go to youtube but I will tell there is nothing about being able to upload a video to youtube that makes the information any more credible than what you will find here.
Most of what I have seen on you tube regarding firearms,ammo,and reloading has run from mediocre,to poor,to downright stupid.
Do yourself a favor.If you want to load good,match grade .308 ammo,find and buy a really good tool(despite the advice against spending money) a book that has a title close to "Precision Shooting's Guide to Reloading for Competition"
It will teach you how to set up your dies not only for head clearance,but for concentricity.
It will also teach you brass prep from the standpoint of most return on the time invested.
It does not serve you to get involved in a whizzing contest.
If you are getting serious about trying to develop your rifle/ammo combination,sooner or later you will become interested in making your accurate,prepped brass last longer.You may even buy Lapua or some other expensive brass.Buying brass and the time to prep it is expensive.A $35 tool that makes your brass last longer is cheap.
I do not know if it is still there,but if you search a bit,you may find a site named Varmint Al's.On that site,you may find an old article on "Finite Element Analysis of Chamber Finish and Bolt Thrust" or something similar.
Aside from the point of the article,is some very good information ,illustrated,showing how .308 brass stretches and thins back at the classic stretch ring location ahead of the case head.It will show % of case wall reduction at .006 or .004 head clearance,iirc,Which may well be where you end up at minimums.
The RCBS mic lets you measure a fired case,and adjust for xxx setback.It also lets you compare to a master round,if you create such a thing.
The bushing die is about $20,and gives you a drop in master chamber,of sorts.
It is the simplest way to dimensional confirm correct ammo.If the necks ar long,they stick out.If it is long (headspace) it will stick up out of the die.If it is short,it will be sub-flush the ground step.If you want,you can measure over the bushing /brass to see just what you have using calipers,mic,or indicator.
If you manage to collapse a shoulder or load very eccentric ammo,the bushing will reject it.
To the bump /crunchers,you can do that.
What is the mfgr of your shellholder?Your dies?Are your dies at maximum or minimum material condition?What about your shellholder?Does Lyman or Lee tolerance their shellholders exactly the same as Redding or RCBS?What are the max/min tolerances on dies and shellholders?
I do not know,but it does not matter,because I do not assume.
With the die at on setting,will you get different results with WW brass,Lake City brass,Rem brass,etc?Yes you will,as they spring back differently.
OP,there is plenty of info here to answer your question,more than once.
Now you get to pan it down to what is Gold keepings,and what is mud leavings.Good Luck!