Adam,
I appreciate the time you put into your reply, but I'm still not getting what you're trying to explain.
The .300 PRC has 94.5gr of H2O capacity, the .300 Norma is 104gr of H2O, both using the overflow method, apples to apples.
If you seat a 225gr ELDM into both, to a depth of .308" on the shank, not including the boat tail, you end up with the same negative volume in terms of capacity, as this is all relative to the case mouth. The PRC has a usable capacity of 86.074gr of H2O, the Norma is 95.570gr. The Norma is more 'magazine' friendly, it allows you to throat the bullet longer, thus out of the combustion chamber, which would be an advantage with the 245/250 class.
Again, if you look at the OAL with both bullets seated to the same depth, the PRC is 3.743" and the Norma is 3.632", a difference of .110". Longer and skinny is better how?Time and time and again, short fat powder columns have proven to be more accurate, 6PPC, 6BR are excellent examples.
Steve,
you are trying to scale up 100-yard point-blank benchrest toy cartridge dynamics and apply them to extreme long-range heavy artillery builds, and the physics simply do not cross over....if it did miltaries across the globe would be knocking on your door!
First, quoting the short, fat powder columns of the 6PPC and 6BR to defend an extreme-range magnum is a total thermodynamic fallacy.
Those tiny cartridges burn small, ~30-grain charges of fast propellants at short distances. When you scale up to stoking 85 to 95+ grains of sluggish, slow-burning progressive powders behind a massive 245gr Berger past a mile, a wide, fat column creates a severe mechanical defect: erratic flame-front propagation. A standard primer blast cannot ignite that wide block of slow powder uniformly across the face of the column.
This introduces microscopic ignition delays and erratic internal pressure waves, driving up your extreme spread (ES) velocity deviations--which turn into massive vertical flyers long before your bullet ever sees the 1,600-meter plate .
The tall, narrow, linear column of the 300 PRC ensures a perfectly uniform, predictable flame travel straight up the axis of the case, delivering the single-digit ES required for vertical consistency at distance.
Second, your 'same seating depth math game walks right into a massive mechanical paradox!
You claim the Norma is 'more magazine friendly' because you can throat the massive 245gr bullet shallow and forward of the case mouth to preserve room....
HOWEVER; if you throat that short Norma case to push that massive 1.775-inch projectile out of the powder room, your loaded COAL stretches out so incredibly far that the round will no longer fit, feed, or cycle through a STANARD long-action receiver footprint or a standard 3.85" CIP magazine!
To run it that way, you are forced to bypass standard long actions entirely and step up to a specialized, expensive, oversized .338 Lapua Magnum-sized receiver core!
The 300 PRC was explicitly engineered from day one to deliver maximum VOLUMETRIC EFFICIENCY under that heavy 245-grain projectile inside STANDARD, affordable long-action rifle dimensions with ZERO mechanical compromises!
The 3/32-inch (0.110") case length difference is exactly the structural runway that keeps the bullet body safely forward of the shoulder while tracking flawlessly straight down the center axis of a standard long action.
Real-world toolmakers headspace from the bore outward, not backward from a benchrest catalog chart!
.... not in your fever dreams, bench top calculations or internet discussions. You use the term, "field mechanics" while denigrating the notion of actually shooting a rifle in the field. 
