I had ordered a reamer from PT&G to be tight necked at 0.401", shortened freebore from 0.750" to 0.250" and the freebore diameter 0.3754". They incorrectly ground the neck diameter to 0.405" which is standard. I was quite upset until I fired a few rounds.
I can still load the Barnes and Sierra's out to touch the rifling if I want because of the short freebore, and they'll work in the magazine. I will find out how the GS Customs fit in the future.
I used Pressure Trace to keep an eye on things, this is the screenshot of this load I am using:
The first shot is a fireforming load using 78 grains H-4350 under a 235 grain Speer using Winchester H&H brass. I believe 3000fps is doable with the right powder and the 235/250 grain bullet. But it would sure make a mess on the receiving end.
Like I said, well below Weatherby max, just under H&H max. It works, so I have no desire to go up, maybe though just to see what the velocity would be at max. This brass is spendy though.
Interestingly the pressure with Winchester brass is around 5kpsi higher with the same load. I weighed a couple cases and they are 20 grains heavier. Hmmmm.
The total time Jim had the rifle was about 9 months. I know any good gunsmith could do the same, but Jim loves the ZKK/CZ's and it shows.