UMP Barrel vs USC Barrel Materials

[CARRYAGLOCK]

The actual UMP barrel is hammer forged and chrome lined.

The HDPS UMP clone barrel is stainless steel to exact HK specs.

But what is the USC barrel?
Hammer forged and not chrome lined?
Also chrome moly or stainless steel barrel metal?

Trying to decide in the wear characteristics and corrosion resistance of a HDPS 7" barrel vs a cut down USC barrel or keep my actual UMP barrel for my conversion?

[AviatorDave]

I'm not sure that a UMP barrel IS chrome lined. It's not mentioned on the HK website, nor in any of the manuals. The twist rate and direction, and number of grooves is specified, but nowhere does it say chrome lined that I can find.

If you have an actual UMP barrel, I'd use that. (And I do as well.)

And neither of them are stainless steel, they're parkerized which doesn't work on stainless. The factory barrels are all alloy steel, possibly 4130 or 4140, or some other high-carbon steel. There are a lot to choose from.

[CARRYAGLOCK]

AviatorDave,

Thanks again! You are a well of UMP knowledge for me!

I asked the chrome lined question because my UMP barrel (real HK) really looks chrome lined. After reading this I looked real close and it's most likely not. The chamber and a very small uneven ring on the breach face is so bright and shinny! I thought it was chrome and the shinny part on the breach face being an uneven circle looked like it was probably chrome plating. But the uniformity of the crown shows the cutter did a perfect job (of course) and left it really bright and shinny too. If it was chrome lined it wouldn't be the perfectly concentric crown it is on the outer edge of the muzzle.

So it's just a really bright and shinny bore, which is a good thing. But not chrome lined.
Which won't matter.