New first...the 45 Colt shot well...to 100 yards, for an open sight, brand new, 150 shots through the barrel of cast 158 gr. LSWC's over 6.5 grains of IMR 700X. The trigger is HARD but is hoped to improve in time. The powder is not working to its pressure limit. The cases were sooty from inefficient closure against the chamber and the barrel was very dirty with unburned powder. But it was fun to hear the bullets impacting on paper and to see the LARGE holes by comparison to the 223.
I just purchased a used 223 and it too shot well with reloads made by progressive press and not specifically for this gun. When the little barrel was on paper at 100 yards, the newly acquired, but used Redfield wide angle scope made punching out the bullseye significantly easy. "Barrel off" shot well, and reducing pressure on the forearm stock screw brought it back and held center BEST. I "danced" five shots around the inside corners of a 1.25" diameter bolt that had been used to pen a bullseye. Accuracy was best with Varmint Extreme 55 gr. lead tipped spitzers. Hornady Vmax polycarbonate tipped bullets were the worst, but that should be attributed to only 4 rounds on hand and the first "set" following the forearm "torqued" to the barrel. More work is in order for the Hornadys. Remington factory 55 gr. lead tipped spitzers also shot well.
A "troubling" aspect of the used 223 was its failure to eject the spent casing. I had to drop a steel bit down the barrel five or six times to dislodge the "stuck" case as the ejector did not function and held fast when the breech was opened. I think that it was a function of the forearm not being on the rifle at the time because the brand new 45 Colt did the same thing, as an extractor, with its forearm removed. However, when the 223 forearm was reinstalled, the failure continued, for a while, to eject the spent case. What the fix for that?