The throats on my model of 1950 target run about .458! So, I do not think that it is just the later model 25-2's. From what I have read here, mine with the oversize throats is not uncommon. Not sure at all about 1917's. My Model 29, approx. 1968 version, has throats that run oversize by about .004. It may have been common engineering to run the big bores with larger throats. All my .357's run mostly right at .357.