Thanks, gents for the replies! I appreciate your input.
Mark, the OBT or Optimum Barrel Time calculation is based on the fact that upon cartridge ignition, a shockwave runs up and down the barrel at the speed of sound in steel, which is very, very fast, like 22,000 fps if I recall. Whenever the shockwave gets to the muzzle, the muzzle vibrates a little, which opens your group up if the bullet is exiting then. The speed of sound in steel is so great that you can get 2, 3 even 5 times where the muzzle is vibrating from that shockwave, before the bullet leaves. So you try to find a powder load that gives the bullet a barrel travel time which hits the "node" when that shock wave is as far from the muzzle as possible.
In the Quickload program, one thing that is calculated for you is the barrel travel time for each powder and bullet and barrel length you select.
There are a number of ways to address this shockwave effect and get the effect lessened, like those Limbsaver rubber things. The BOSS system is another way to tune your barrel to a particular powder by changing the effect of the shock wave. Basically if you can dampen the vibrations your rifle will "like" a broader range of loads.
Old school fine rifles used to have the barrels bedded pretty firmly in felt, to dampen these vibrations too. I don't know if the old timers knew why it worked, they just knew it worked.
It is why some powder types shoot better than others even though the velocities are similar. A hotter powder seems to have a shorter barrel time with the same muzzle velocity.
It is also why often you need to back off from max load to get best accuracy. In my Tikka, for example, a max load 180 Partition PP is not accurate because it is leaving the barrel while that harmonic is at the muzzle. I have to back it down quite a bit for best accuracy. But those 165s look like they will get out fast enough (barely) using RL 17 to hit the next node.
If you are interested I have a link to the website of the guy who published his research on this, and an Excel calculator for barrel lengths and their best OBT.
Barrel diameter doesnt matter either, though stiffer (thicker) barrels have less of an unstable spot because of their stiffness.
I've found in real life using the calculator and QL and a chrony that it is remarkably accurate at getting you within a half grain of the best accuracy with a given powder, bullet and barrel. Then I do a ladder or OCW to find the absolute best, and hope the temperature etc is close to the same when I go hunting
Luke, I would not think a Game King would be a good bullet to shoot super fast at short range at a big animal. What cartridge was it in? A 165 GK hot loaded in a 300 WSM or 300 Mag ought to be going about 3100 fps at 80 yards, that is a lot of terminal energy for that bullet I would think. It's why I am looking at the tougher bullets for the 165 gr. load.
Like i said, currently 400 is a real long poke for me these days, I am way out of practice. Luckily I live 20 minutes from the BOTW range in Liberty Hill. Looks like i have my work cut out for me, soon as I get that 6.5 lb Tikka braked!! I developed a heck of a flinch working up hot 180 grain partition loads for the last hunt..... 25 or 30 rounds and it was a day....