Is there a difference between today's .32 Auto ammunition and the old .32 S&W ammo that the pistol originally used?

Very little I would think.

.32S&W? In a semi-auto?

As far as I know, the old Colt should only shoot .32ACP. Assuming I'm right, today's .32ACP is most-likely loaded to a lower pressure than the old stuff, so you should be OK with it, if the pistol is in good condition. I shoot a late-1930's production Walther PPK, use WWB or anything else that's on the shelf, if I'm too lazy to reload.

If you're concerned, get a set of replacement springs from Wolff.

Just to reiterate: Your Colt 1903 is chambered in .32 ACP (aka .32 Auto), NOT in .32 S&W. Those are two different, incompatible cartridges.

The below photo shows the five most common .32 caliber handgun cartridges. From left to right, they are...
.32 ACP - .32 S&W - .32 S&W Long - .32 H&R Magnum - .327 Federal Magnum


Besides .32 ACP, the others are all revolver cartridges.

quote:

Originally posted by newtoSig765:
.32S&W? In a semi-auto?

I’m confused too.

The 32 Smith & Wesson round was a rimmed cartridge designed for use in revolvers. According to my Cartridges of the World, the 32 Automatic Colt Pistol (ACP) that Wikipedia says the Colt 1903 was chambered for is a significantly different cartridge. The 32 ACP or 32 Auto is still offered by a number of manufacturers.

Added: RogueJSK beat me to it.

I have shot .32 S&W in a Walther PPK! My Dad brought a Walther PPK as a war souvenir from WWII.
As a preteen/earlyteen, I told my Dad I wanted to shoot it. Well, he went down to the local lawnmower, bait & tackle, outboard motor, and gunshop, asked for box of .32's. He got a box of .32 S&W.

We went out to a local range, loaded it up and bang, it fired! It did bind up in the ejection port. Confounded, we cleared it and tried again, same result. We somehow then figured out the reason. I don't remember how we determined the reason, but that ended the shooting session. We may have had a partial box of .32 ACP for comparison.

I now have that PPK, and that box box of .32 S&W. The price tag on that box $3.45 (circa 1966-67).

Well, I have egg on my face.

I've shot the 1903 quite a bit and had used both .32 auto and ACP in the past with no problems. I posted the question after finding a VERY old box of .32 S&W and thinking I may have shot that through the pistol as well. What I think happened is that my grandfather may have also owned an early S&W revolver and the ammo came from that.