Most of the group of folks that I know that shoot BPCR weigh each and every charge. Some don't, most do. It is a matter of repetitiveness. While minute of whitetail deer won't show any velocity deviation, paper targets will, especially once you start moving to 200 yards or better. Velocity variation will show up as vertical stringing.
Some of the folks (well more than some) even go as far as to weigh each and every bullet and each case. Case weight variations will help pinpoint internal volume discrepancies which will affect the burn.
I have seen .003 to almost .007 (maybe more) variation (high to low) in case web thicknesses in the same brand of brass, but in a mixed lot, in some cases I was given. This will affect the degree of compression and cause a difference (well slight) in the burn, especially with BP.
NOW with that said, there is a group of folks that shoot muzzle loading slug guns at a club near me. (Canal Fulton Ohio). I have seen those folks shoot 100 and 200 yard groups you could cover with a half dollar and all they do is drop their powder charges with a measure such as the old Belding and Mulls.
My Belding and Mulls will consistently drop within a couple TENTHS of grain of BP as long as I actuate the lever in a consistent repetitive manner each time.