With my relatively short time trying to get rifles to shoot well with cast bullets, and that time includes being surrounded by others that have been doing this a long time at Wilton, the points made above about different rifles/bullets/loads might require different methods and parameters to arrive at satisfactory results certainly rings true. And like pretty much ever sport/hobby out there, there are a million opinions on what works, what you should do, why things are doing what they do, etc., etc.. All one can do it try to absorb it all and then weed out the BS from fact thru either logic, experience or further research.
I tend to believe that one of the pitfalls of any hobby is that people will draw conclusions and make broad applications for that conclusion. I know I've done it. It seems to be a pitfall because we are all looking for the secrets to be revealed.
I personally never really gave the throat of a rifle much thought. It's always been the groove and bore diameters and twist that I looked at to determine what my bullet needs to be. But looking back, when I started shooting my 03 using .310 sized bullets for what I expected to be a 0.308 groove diameter, I noticed that the necks were always coming out jet black. I'd never seen that blow-by before since I was never into milsurps or old rifles. I got comments from others that milsurps tend to have big throats so the rounds will always chamber and other rationalizations. But I would walk the firing line between relays and not see cases that looked like mine. I'd come here to lament my situation and got help and several suggestions as to why my rifle simply would not shoot well. Someone here even sent some wax for me to try in making a better lube.
I slugged my barrel, which I did several times because I did not believe what I was seeing, and when I saw that the groove was 0.311-0.312, I thought my barrel was shot out. I was considering putting a new barrel on the rifle. But it was Perry, the old guy with the shot-out Enfield that opened my eyes. He's a very pragmatic old guy and does not mince words. We shot together at a match one day and he was shooting his oversize Enfield. He said he thought that I did not need to rebarrel the 03, just shoot fatter bullets. He had 2 or 3 rounds left from the match and offered them to me. My scope was set for 500 yds and his bullet was a similar weight. I shot at a bowling pin sitting on the berm. To my surprise, I hit it with all the rounds. I could not believe it. He had gotten my attention. After that day, I pulsed all the guys for a mold that dropped a .314 bullet, including Charlie's vast collection. I found one and damn if it did not turn that rifle into a shooter. I ordered a mold from NOE for a .303 British that dropped a 0.314 bullet and everything changed. First, the blackened necks went away. But more imporantly, the rifle began to shoot. Did a ladder test and settled on 17.0 gr of 2400 and have been shooting that since with great success.
So, now the question is, was it filling out the groove diameter that did the trick, filling out the throat or both? My guess is both. But I really hadn't considered the throat playing a part until it was mentioned in this thread. I guess I never viewed the blackened necks as an indicator. I might have been able to use just that info to tell me to up the bullet diameter and arrived at the same point.
This is a good discussion. It's really why I come to sites like this. All the friendly BS is fun and such. But it's the sharing of knowledge and experience that is the true value to sites like this.