Ok, here it goes. I picked up two older Smith and Wesson revolvers a few years ago. I never shot either one but did plan on it later just never got to it. I was collecting heavily at the time. One came with ammo and the other did not. The previous owner never shot them either.

Revolver #1 is marked:
38 S&W Special (Is this just a .38 special?)

Cylinder length: 1.5625

Chamber Diameter: 0.3810

Chamber depth: 1.15 Roughly (I stuck a tube in till it hit the part where the brass would stop, cut it flush with the back of the cylinder, and then measured the tube. Not exact obviously.

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Revolver #2 is marked:
.38 S&W CTG

Cylinder length: 1.5625

Chamber diameter: 0.3810

Chamber depth: 1.15 Roughly (I stuck a tube in till it hit the part where the brass would stop, cut it flush with the back of the cylinder, and then measured the tube. Not exact obviously.

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Now here is my confusion. The chamber diameter for a 38 S&W should be 0.3855 or a tad bigger as .38 special and .38 S&W are not the same round. The cartridge diameter of a .38 Special is 0.379

I have both ammo types as the one marked 38 S&W came with ammo marked as such but it does not fit in the cylinder. However, .38 special fits in both cylinders and it ejected by the push rod in both revolvers.

What is the likelihood the 38 S&W got a cylinder swap to .38 special? I think this is the case based on the chamber measurements nothing else fits those dimensions.

I went and checked and there is a clear ledge where you would expect the brass to touch.

Good to know.

Now what do I do with 11 boxes of 38SW ammo.

38 S&W sits in between the 38 colts

.38 Short Colt:
Bullet Diameter  .357 in
Case length        .762 in
Cartridge length 1.052 in

.38 S&W:
Bullet Diameter   .361 in
Case length        .780 in
Cartridge length 1.200 in

.38 Long Colt:
Bullet Diameter   .357 in
Case length        1.030 in
Cartridge length  1.320 in

Thanks for the replies and the valid points to consider.

I think I will test them both with 38 special rounds using a string and cover on a private range and see how they do.