Greg:

As you say, I don't think you understand the relationship of lands to grooves in terms of accuracy.

Lands grip the bullet. If the lands are of proper dimension to adequately engrave the bullet and the barrel is otherwise true, the groove depth can be of somewhat "overbore" diameter and still produce a rifle that shoots well, until the lands wear. At the point of substantial land wear, the groove depth will make a difference more noticeably, with accuracy deteriorating quicker than if the groove depth was of bullet diameter.

Rifling FORM matters here as well, as I stated in earlier posts on this thread. Narrow lands wear quicker. And if they start off on the high side of diameter, all the worse.

Regardless, the point being made over and over again is that excessive groove depth of .002 is highly unlikely to result in poor accuracy ON ITS OWN.

And then again, what is "poor accuracy"?

The No.1 rifle is known to be at times a tricky rifle to make shoot well. They have that reputation and have since they were first made. Such groups as 3" for 5 shots at 100 yards aren't too uncommon, with load work and bedding attention addressing the desire for better groups. In that respect the design IS "suspect", just as is the design of any two-piece stocked rifle.

COULD Ruger have made a barrel to .311 or .312 or .313 diameter across the grooves?

I suppose they could have, but they didn't IN YOUR RIFLE'S CASE.

Is that alone sufficient to make the rifle unusable? No.

Does such boring stand outside the realm of normal for .303 rifles, military or commercial? No.

Now, to put it another way, you suggest a groove depth of .313. Why? Why not .312 or .311? Or .314?

Let me be clear. I do not know what the specification for production diameter for Ruger .303 barrels is. I sort of doubt it is .315 or we would have barrels on the high and low side of that, likely, depending on how many are made. Remember, rifles are not "made to a certain bore diameter". I think that is where you are missing the point. Every barrel made by a company is not necessarily "ON" with any variance resulting in the barrel being scrapped.

Barrels are made to a certain bore spec, plus or minus. So your rifle is .315. I suspect there are Ruger .303's that have .314 or .313 barrels also just as there are military rifle barrels that vary. At some measurement, the barrels would be scrapped. With military rifles that measurement was .3205. That is the point I was making long ago in this thread. .315 might not be ideal, but it likely falls within reasonable production standards set by Ruger. Barrels often fall outside the optimum and folks don't even know it, because accuracy doesn't show it, because the tolerance is not great enough to matter. And such is likely the case here.

You may have a "wide" barrel. Somebody else has a "narrow" barrel. What the exact tolerance for Ruger barrels is I do not know and I doubt they will tell you. And maybe the production run was so small all of them are .315, because .315 fell within the established, time-honored, established norms for production .303 barrels. Thus, I doubt the boring on your rifle falls outside accepted norm for factory production rifles. If you slug a bunch of gun barrels you will see just what I mean here. Just because a .30-06 is a ".308" doesn't mean it is...

I hope you are able to get the problems solved, and for your own peace of mind it would be nice if Ruger rebarreled the rifle for you, but will that solve the problems? Maybe, if the barrel is lame in some other way. The mere extra .002 of groove depth is highly unlikely to be the culprit.