Tight chambers common on same gun model ???

[Magnum Wheel Man]

been playing with these old top breaks & Trailboss powder with both the 32 & 38 S&W's... my original expiriements were using Hornady .315" round balls for the 32's...

... I reciently bought some Hunters Supply 76 grain .313" flat points... I had to bell the brass more for the bullets over the round balls, & adjust the seater die... the case is slightly buldged where the bullet is ( I could maybe use a slightly bigger expander plug ) but the loaded rounds slip easily into all of my 32 S&W chambers except one... a Hopkins & Allen Safety Police Snubbie, that has been shooting exceptionally well with my round ball loads ( & I mean really exceptionally well )... I have a couple other safety police models of similar vintage, that these bullet loads easily slip into...

so, was it really that common to have guns with different chamber diameters on these guns built around 1910 or so ??? when guns that would have come off the same tooling line had bigger chambers ???

I'm not complaining how the one with tighter chambers shoots, but because it's a snubbie, I was hoping it would should the bullets as well as it does the balls...

... maybe this isn't really that uncommon, as I reciently got a pair of new Ruger Montados that had tight cylinder chambers...

 

[James K]

Chamber diameters vary today on all makes of firearms. For example, I have several Colt and S&W .38 Special/.357 Magnum revolvers; some will accept .38 S&W, some will not. Some will accept .38 S&W cartridges from one box, but not from another.

All chamber dimensions have tolerances (usually ignored by the loading manuals and cartridge books) so any given cartridge will have a diameter of, say .365" +/- .003" and its chamber will have a diameter of .370 + .003", so the maximum size cartridge (.368") will always fit in minimum chamber (.370"). But the minimum cartridge (.362") will be quite loose in the maximum chamber (.373"). (Of course, this doesn't refer to any real cartridge or chamber, I am just making up some numbers.)

The reason is practical machining. Chambers are cut with a reamer. To get its money's worth out of a reamer, the company makes it oversize (to the + side of the tolerance). As it is used, it wears and is sharpened. This may happen several times before it is at the - side of the tolerance, when it will be discarded. So your "tight" chamber was cut with a worn reamer; a "loose" chamber was cut with a new reamer. Could chambers be cut to a precise dimension? Sure, but then a new reamer would be required every few uses, and the costs would increase considerably. Even if the chambers were precise, the cartridges would not be, so the chamber would have to be at the max or some cartridges would not fit. Of course the reamer business applies not only to chambers but to the dies used to form cartridge cases, the dies used to size cases in reloading, etc.

Some folks claim that they ream chambers to a precision not attained by mere mortals, then measure or even make cartridges so that every one is a perfect fit. I hope they are happy; I'll spend my time in some less taxing pursuit.

Jim