The 4.1 IMR TARGET in middle area means "4.1 grains of IMR TARGET".
The brass with the highest internal volume was the lowest velocity, because it was lowest pressure? The brass with the lowest internal volume was the highest velocity, because it was the highest pressure. And look? The mixed brass, which we purposefully had a large range of low capacity and high capacity cases? landed right near the middle generally. Right where it should be.
So...what is the take away? If you need more case capacity because the powder you are using is bulky and you worry about too high of pressure? Get some brass that has very high case capacity, it will help! If you are shooting lower power rounds, then just get any brass.
What is the other takeaway from this entire page?
If you find a powder, like we did, in IMR Target, that shoots good groups across a range of loads near each other....and they hit generally the same area of the paper at say..10 yards...then mixed brass can work very well.
But what if your powder doesn't group well across this range of near loads? Is mixed brass terrible? Don't even think about it...we have that test too...its coming!