.357 Casings Getting Stuck In Cylinder?

I recently bought a box of .357 (found a deal, $25.00 for 50 rounds) to run through my Sauer & Sohn Chief Marshal .357.
Mind you, I've shot .38 Special through it without a problem.
I tried out the .357, all shot fine, but when time came to remove the spent casings, two became VERY stubborn to release. I pushed the ejection rod, casing came out about 1/4" to 1/2" and stopped.
Tried pushing it back in, it was STUCK.
Luckily, we had a hammer and a brass punch handy and were able to lightly tap out the casing after removing the cylinder from the gun.
Casing had all kinds of scrape marks on it, didn't look blown out in any way.
I tried running another six through it, and same thing, except on more than two of the casings, I believe 4 of 6 did it.

Does this sound like bad ammo, or do I need to take my cylinder to a gunsmith and get it polished or something?
Again, like I said, .38 Special goes through with no problem.
The brand on the ammo is Remington UMC .357 Magnum 127 grain JSP (which I found odd, as my .38 Special ammo is usually 132 grain, different brands, not Remington UMC)

I am VERY meticulous about the cleaning of every component of this gun, as it was passed down to me by my father; are you sure that's the most likely culprit?
Only 6 .38 Specials were fired prior to loading the .357.

USSR said:

Like Brian said, after firing .38's in a .357, you've got to clean the chambers real good before using .357's.

Don

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So one cannot switch from .38 to .357 while at the range without these reprocussions? I guess I could go and shoot .357 and see if I get similar results without using .38 Special first.

Any idea why you need to clean before using .357 after using .38 Special? Aren't the case dimensions the same, except in length?

W.E.G. said:

Plain lead bullets with goo-lube are the sure-fire recipe for this sort of problem.

If you must shoot .38's in your .357, stick with .38's, or at least use bullets that don't have goo-lube on them. That goo-lube turns into something that resembles epoxy when combined with high-pressures and burning gunpowder.

Somebody will be along shortly to tout the wonders of the "Lewis Lead Remover." Looks like a great tool if you can actually find one. Brownell's lists them, but they never are in stock for .38 caliber.

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Goo-lube?
This is the ammo I'm using, not plain lead though.

W.E.G. said:

The goo-lube residue was probably already in the chambers.

The jacketed-ammo rounds just gave the goo-rings a fresh coat of sticky carbon.

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What is this goo-lube that keeps being mentioned? I thoroughly clean this cylinder with quite a bit of Breakfree, running patches through until I get clean ones.