Parashooter,
We have discussed this before does not hurt to do it again, thanks for the chart. Interesting that the 2 straight cases that I see 45/70 and 30 carbine show the same pressure for both styles.
303 and 308 with very similar powder capacities are 9 and 15 percent different.

With the Krag in the ad we do not know the actual bore size, if it happened to be .307 just a fuzz on the tight size the pressure could be a lot different than the 45/49 for 303 standard commercial ammo.

Proof rounds were mentioned at 70K. One proof pressure test in old riveted boilers made them stronger by shifting all the rivets till they were bearing evenly. Without the proof test only a couple might have had a load, when they failed the next tight ones would bear the load till they failed, pretty soon you get a catastrophic failure at what should be a safe pressure. I think the same principle applies to the proofing of the original Krags, the lug surfaces have slight angles on them, proofing would mush the surfaces slightly so that a higher percentage of those surfaces were bearing the load. One advantage the rifle has is normal wear would help the surfaces mate over time without proofing. Constant repeated overloads can not be good for a boiler or an rifle.