Re: 300 wsm case capacity question.
Case capacity has often been difficult to deal with. And there's several ways it gets measured, too.
For example, a new case at minimum dimensions will have a smaller volume inside than a fired case from a chamber that's at the large limits of specs for the cartridge chamber dimensions. And after the fired case is sized, its insides will have less volume because parts of the case have had their dimensions reduced.
And depending on how case capacity is measured stirs the pot, too. Some folks measure it by filling the case with water all the way to the mouth. Others only fill it to the neck-shoulder junction.
I'm pretty much convinced that cartridge brass is about the same everywhere. So, the best way to measure case capacity is to measure case weight. Those weighing less will have less volume to subtract from chamber "capacity" or volume. Note the case expands hard against the chamber body, shoulder and neck walls as well as the bolt face. It's when the case is bulged out as far as it will go with 60,000 ppsi it its true capacity/volume realized. Measuring case capacity by other ways ain't gonna result in the real case volume when it's firing a bullet; and to me that's the volume that counts.
Which means you've only got so much room inside a case. You can fill it with different amounts of powder and bullet. I don't think 1/10th of an inch deeper bullet seating will change things much. As long as the bullet jumps the same distance to the lands all is well.
I've worn out several .308 Win. and .30-.338 Win. Mag. barrels and a .264 Win. Mag one. Through their life their throats eroded such that the bullets needed to be seated out at least 1/10th of an inch to still touch the rifling when chambered. Accuracy was excellent throughout the barrel life. I knew when the barrels were about to go bad when I needed about one more MOA elevation on the sights at 600 yards on the same range with the same load due to muzzle velocity getting lower with more throat erosion but accuracy was still great.
I don't think your shorter loaded rounds will cause any problem. If they don't shoot as good I think something besides case volume is the culprit. Who knows; they may well shoot better.