Matt,
A few things come to mind here:<ul>
<li> In evaluating some of the commercial "cowboy" loads recently, we found that few of the manufacturers use bullets harder than about BHN 12, consequently you might get some leading out of your No.1 if the bore isn't pristine.
<li> Did you thoroughly clean all the jacket fouling from the bore of your No.1 before shooting the cowboy ammo through it? Those guns are proof fired at the factory, and not cleaned prior to shipping (at least properly), thus there is residual jacket fouling in the barrel. Jacket fouling coupled with lead bullets that already have a tendency to lead in a sure fire way to get a soldered bore!
<li> Did you go through a proper break-in procedure with your new No.1? Simply going through the tedious but necessary steps to break in a bore can greatly aleviate both jacket fouling and leading in barrels.
<li> Your observation of the tight spot under the barrel band is entirely correct. These guns respond remarkably well to fire-lapping. Not only do they have a tight spot under the barrel band, but where the wonderous warning label and other inscriptions are roll-stamped on the left, rear side of the barrel you will most often find a mild constriction in the bore there as well. Fire-lap that rascal!
<li> Finally, our experience has shown that the throats in these guns while being short, are fairly generous in diameter often running .461-.4615" in diameter. Tests that John Taffin ran in the Ruger No.1 .45-70 Govt. showed our .460" diameter 405g LFNGC bullets to be absolutely the tightest shooting of all ammo he ran through his test Ruger No.1! .460" Diameter bullets are the key to best results using cast in your new gun!</ul>
Hope these items give you a starting point to look for the culprit robbing you of accuracy, and adding to your barrel cleaning misery!
Let us know what you find!
God Bless,
Marshall