I own one #1 in 9.3X74R and it's every bit as accurate as the 375 shown above. In fact my best groups are about 1/2 of what his 375 is doing. It has become one of my favorite hunting rifles and I have killed a bunch of game with it.
I had a 270 years ago that was also a super good shooter. 5/8 to 3/4 was what I could expect.
I had two #1s in 243, one shot about 1-1/4"consistently but the other shot about 4". Sometimes it would shoot 2.5" but you could not bank on it. I was going to re-barrel it but a friend wanted it for a project gun so I sold it to him cheap. Both of my 243s were made in the 70s
So #1s can be hot or cold as far as how they shoot. I do not hear the complaints of inaccuracy today that I used to hear 25-35 years ago. The older ones had Wilson barrels in them, and the quality was all over the place. Some very good and some very bad. Later they used Green Mountain blanks with FAR better results, and I am told now they use barrels of their own making, also quite good.
I worked on a 22-250 for a friend in a neighboring town and he thought it was a lemon, but we found it was just finicky as to what loads it likes. I tried a few different powders and charge weights and it came right in. So that one seemed inaccurate at first, but it really was not. With the right load it shoots about 3/4"
