Unfortunately, you don't get to know what powder is being used in Factory ammo, so you will have to depend on the manufacturer to continue to use the same powder for as long as you shoot it.
I believe Federal used both Reloader 15 and IMR4064 powders at different times in their FGMM 168 grain .308 ammos so manufacturers may change powders depending upon availability and cost at times.

At least, when I run out of a powder and can't buy the same powder, I can note the difference and gather the data for the new combination.
And different powders obviously will produce different results with the same bullet.

The barrel will still tell you what it shoots best, manufacturer to manufacturer, at the same bullet weight. No two manufacturers will probably be using the same powder, even if they are using the same bullet.
Example, Federal GMM and Black Hills use Sierra SMK bullets in different bullet weights and Federal also makes FGGM with Nosler CCs (or at least they used to).