Ed, all I did was change the shoulder angle and remove some taper, in this case to 45°. Probably a bit extreme but it feeds well from a Hawkins Hunter mag with the 130 TA.What improvements did you end with, sharper neck angle/shorter neck, etc.? Those velocities out of 21" are no slouch.
I have to single feed the 144 LRHT. Long story short Manson built my reamer with the wrong freebore so it seats long. I haven't tried it with the 156 EOL yet.