Aliant do not have load data in their online Manual for the Berger 168 Hunting VLD's. It is most likely that the guy is pushing pressures to the max which is pretty high in the WSM case, I believe 65000PSI. In any event your brass will last much longer if you find a load in the 3000- 3050 range and the deer or moose won't know the difference.
I have been finding that case capacity and hardness of the brass can vary a lot from brand to brand and even lot to lot. I believe that there was a thread on this a while back. I have done extensive testing with a number of 223 brass converted to 20-223 Extreme and found this can lead nearly 100 fps difference in velocity with the same load in a hard case, with less capacity, compared to a softer one with greater capacity.
I have been working on finding a load for a friends 270 with IMR 7977 and the 150 Nosler LRAB. The first thing I learned was that I could not get within 0.200" of the lands at 3.440" OAL which over the Saami Max of 3.340". Hornady show a Max load of 60.8 C doing 2940 fps with Winchester Brass but I only had one brass and a whole lot of FC brass which only held 58.1 grains under the bullet and a compressed load at 58.7 grains got a dismal 2747 fps. I filled the Winchester brass with 58.7 grains and got 2748 fps so decided to find some Winchester brass and run with the compressed load.
A friend gave me a pile of once fired brass and we also had some Hornady and Nosler factory rounds. What I noticed right off was that the new brass measured about 0.465" or less at the base and that none of the brass came close to fireforming to the Saami Max Cartridge measurement of 0.4698" or Saami Min Chamber dimension of 0.4708". In fact the Hornady brass measured only 0.468" in spite of the primers flowing 0.003". Based on this and the fact that the RCBS FL die sized the base datum to 0.4686" I determined that I would consider a fired base datum of 0.4696" to be MAX Pressure with the FL sized Brass.
I compiled a spreadsheet showing brass weights, capacities, velocities and base measurements. I used Ramshot X-Terminator to measure capacities as it flows and weighs nearly the same as water. It has been a real eye opener to me especially in regard to fireforming brass which would take much more than the 61,000 PSI that these 2900 fps loads are generating.
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