Throatdoctor
That's me... I've done somewhere in the neighborhood 100 Ruger .45 throats in the past year and I would like to make a few observations if I may.
First of all the history as I understand it is that originally Ruger made their throats too big. People complained, and they over compensated by making them too small. When people complained again the official stance was, "You wanted them tighter, that is what we did". I honostly don't know exactly whan this change occured, but it was quite a few years ago.
What throat tightness does to accuracy: First of all the purpose of the throat is to convey the bullet into the forcing cone where the "funnel shape" centers the bullet in the bore and squeezes the bullet down to exactly the groove diameter. It the throat is tight, the bullet is "arrested" while pressure builds and then the bullet is squeezed down to pass through the throat and then it enters the forcing cone already smaller in diameter than the groove diameter of the barrel.
Another factor not mentioned above but just as important, is inconsistant throat diameters within the same cylinder. It is not at all unusual to see a cylinder with throat diameters varying from say .4497 to .4512 within the same cylinder! When I see a cylinder that has one throat significanly tighter than the others, I can pretty much predict that when that chamber fires it results in a 10:00 o'clock flier. That is because the recoil impulse begins before the bullet leaves the barrel. The tighter throat holds that bullet back just a small fraction of a second longer than the other throats so the bullet leaves the barrel later in the recoil cycle.
Why the inconsistancy? I don't know for sure but my guess is the factory uses a fixture that bores all six chambers at the same time. When one of the reamers in this fixture reaches some minimum specification it is replaced therefore you can have six different diameters within the same cylinder.
Throat roughness. There are a lot of tool marks in a Ruger throat. But in all fairness to Ruger, there is not a lot of finishing and smootheing done on the parts that are not normally visable. Ruger makes a finely engineered and very strong revolver at a very afordable price. They do this by keeping labor costs to a minimum, therefore minimal finishing. I have foung that if you disassemble their single actions and simply polish the internal parts it can make a big difference. If ruger did this for you, you could add a couple hundred dollars to the price tag.