Here is where a lot of threads go into swirl because the shooting world has a variety of contexts where the answer for a heavy section barrel on a stiff action in a stiff stock, is different than the answer for a thin flexible barrel in a flimsy action and a flexible light stock.... so keep in mind that some answers are based on one end of the spectrum or the other.... Carry on... YMMV
@KMW 1954
I left out a key concept in my statement above, that is, the design of the chamber, throat, and rifling also have a strong impact on what happens. One has to put the discussion into context with respect to the design and quality of the barrel versus the likelihood that the barrel and gun can even produce a group at all or make it obvious that one change in a load variable can make a significant change in the group.
When I was young, the factory barrels of Weatherby's magnum hunting rigs had long freebore. You could not seat a bullet out that far but that wasn't the intent anyway. Those design features were intended to increase the margin against high pressure while allowing high velocity for hunting rigs.
The other popular brands had a variety of chambers and person had to know what they had on a factory barrel. In theory, they had some say in the matter when the barrel was replaced. A hammer forged barrel from Remington wasn't always the same from two different eras even when discussing heavy barreled varmint rigs.
Custom barrels tended to have less scatter in their outcome, that is, when fed the bullets and recipes they like.
The lack of what I will call standardization forward of the neck meant that the results of seating depth searches on off the shelf sporting rifles was a crap shoot.
Sometimes, the results are good but not put in the proper perspective. When the baseline expectation is not kept in perspective, a good grouping for a given context is viewed as 'bad" or "no effect", when in fact for that system the results are as good as can be expected in the composite results for that design.
When it comes to "seeing the difference" and using small samples... Guess which context, off the shelf lightweight sporting, or heavy high quality custom match gun makes it easier to see group size changes... ones where the baseline is to divide by 2 MOA or the ones where you divide by 1/4 MOA?
Try to keep in mind, off the shelf lightweight sporting barrels may seem like they are not responding when they in fact are. This is easy to prove when the rigs are fed ammo they don't like versus ones they do, but the perspective can be thrown off if we are splitting hairs between small changes in what is as good as that system will do, versus not seeing any changes because the gun is already doing as good as it ever will.
We would all like every barrel to shoot small. Fact is they don't all compete if we are talking BR and many will also not cut the grade when talking highpower or F-Class. The context is important, the chamber details are important, and so is the concept of diminishing returns as the rig shoots as good as it can.
A change in the recipe may not show when you are bouncing up against the lower limit of the gun's potential. It may be easy to see a 1/2 MOA difference from a seating depth change in a system with a 1/4 MOA potential, but finding that difference in rigs that shoot 2 MOA is hard with small samples. Best to know which discussion you are in up front. Carry on. YMMV
Merry Christmas.
