Critical Dimensions
Having had considerable reloading experience with all eight of the above Colt SAA calibers I’d like to pass on some personal comments. Colt seems to have always had a problem mating barrel and chamber mouth dimensions. Early on in the black powder days .45 Colt caliber barrel groove diameters were usually .454″, but I have personally measured chamber mouths as tight as .449″. When Colt brought the round back in 1956 they reduced barrel groove diameter to a nominal .451″, although I must say many I have measured are closer to .450″. Conversely every 2nd or 3rd Generation cylinder’s chamber mouths I have measured are at least .455″. I count this as the main reason.45 caliber Colt SAAs have never had a reputation for fine accuracy.
This mishmash of barrel and cylinder dimensions was not limited to .45 caliber. I’ve experienced .44 WCFs of the black powder era with chamber mouths as tight as .424″ with barrels of .427″. More recently I’ve owned 3rd Generation .44s (.44 WCFs & .44 Specials) with chamber mouths as large as .435″. Barrels uniformly have always been .427″ in my experience. Here’s an anomaly though, those 2nd Generation Peacemaker Centennial Commemoratives in .44 caliber have .429″ chamber mouths, again in my experience.
The other two “WCF” Colt calibers also suffered from this ailment. It’s not uncommon to encounter early .38 WCFs with .403″ barrel groove diameters and .400″ chamber mouths. The very first .32 WCF I personally owned had a barrel groove diameter of .314″ but chamber mouths of .310″. I have not experienced a 3rd Generation SAA of .32 WCF caliber so I cannot comment on them. However, I have owned many chambered for .38 WCF, and at this point Colt got things just perfect. Their barrel groove diameters have all been .400″ and their chamber mouths have been .401″.
Having measured fewer .38 Special and .357 Magnum Colt SAAs, all of 2nd or 3rd Generations, I’ve never discovered this non-matching problem. They have all had barrel groove diameters of about .356″ and chamber mouths of about .357/.358″. That probably explains their superlative accuracy potential. In fact the most accurate non-target grade revolver I’ve ever encountered was a 2nd Generation Colt SAA with 7 ½” barrel. Once I did a test of revolver chambers by shooting five, five shot groups with each chamber and then five, five shot groups using all six chambers randomly. Range was 25 yards, ammunition was Remington 148-grain factory wadcutters, and all shooting was done from machine rest. That .38 Colt averaged about 1″ for all 35 of those five shot groups!