I have just been reading Townsend Whelen from the "The American Rifle" (1918), and found it interesting that he reports the common inaccuracy of the Ross sporting rifles chambered in .280. He found it unusual for a .280 Ross to shoot less than six inch groups at 100 yards, and sometimes as poorly as 12 inch groups.
He says that it is because the bore is mismatched to the bullet size in factory ammunition, but they continued to make them this way despite such reports. He mentions there is no such issue with the Ross sporting rifles chambered in .303 which can be highly accurate.

To put this into context, for all the rifles he mentions throughout the book, a good group was 3.5 inches at 100 yards, and 4 inches was acceptable for a big game rifle. A rifle that shot a 2 inch group in 1918 was especially accurate.

I think it is certain that there have been great strides made in the accuracy of ammunition since then - because I have had many old rifles that shot quite well indeed, so it must have been the poor ammo of the times.