Like the 375 Allen I guess. I don't know what Kirby uses for a shoulder angle or shoulder diameter. I talked to Dave Kiff at PTG and he recommended a 33-35*shoulder and a .562 shoulder diameter. So I'm going to go 35* and .562. He said the 33-35* shoulder angle has been proven to be more accurate when he tested them than the 40*. I'll do a .338 version later too as I have 2 Stiller actions coming.
I intend to try the CE copper bullets between 300 and 330gr and I have 260gr Accubonds I can try also. It depends on how much CE wants to do a custom order but I might have them make me brass bullets designed after the copper bullets. So high BC but lower weight and higher velocity.
I just got my barrel Thursday. It's Krieger 10" twist 1.350" shank for 5.5" straight taper to a 1.1" muzzle at 28". It should make the rifle just under 16lbs. It has to be under 16lbs to hunt with here.