I had a chance to shoot my 284 brass. Using LG and Rem 9 1/2 primers I got:
36.9 gr LG averaged 2163. SD was acceptable so I did not record that.
37.4 gr LG averaged 2190. SD was acceptable so I did not record that.
On brass shrinkage:
I started at 1.70. I had new brass and once fired brass cut/trim into 450 BM. I got the once fired brass as such, but I am sure it was fired more than just once.
The once fired brass did not shrink at all.
The new brass shrank ~ 0.003 when fired at 2163 fps.
The new brass shrank ~ 0.005 when fired at 2190 fps.
Accuracy was good for me. I will shoot a deer or zombie any day with this. I shot 35 rounds total and I did have a couple of the new brass rounds fail to fully chamber after a fired round, but they chambered fine after that. They did have a slight bulge to one side, so it was probably a canted bullet seating issue. Fun project and I learned alot.