H&K USP45 black shell casing

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teejhot.40cal

New member
So I just acquire a USP45 and was pleasantly surprised on how the weapon handled. One thing I did notice is that that shell casings were turning black. At first I thought it was because of being winchester white box so I tried some of the hornady defense ammo and it turned black as well. While it doesnt seem to be affecting the performance of the weapon, I would still like to know the cause.
 
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Uncle Malice

New member
Couldn't say. Mine doesn't do that. Clean it thoroughly, put 500 rounds through it and see if it's still doing it.

Does the 'black' rub off of the casings? Is the gun new or used? If it's used, I would guess someone was shooting steel cased ammo through it, which doesn't expand like brass cased ammo and allows the chamber to get caked with carbon... so then if you go running brass cased ammo through it, the brass cases will expand against the chamber edges and rub off the carbon....

That seems like the only logical explanation.... pictures might tell us more.

I certainly don't think it's anything to worry about... but I'd give the chamber and bore a good scrubbing.
 
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TunnelRat

New member
Is it just on one part of the brass? Could be burning powder coming back underneath the brass. Happens on my Glocks. HKs usually have tighter chambers but idk.
 
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marine6680

New member
Happens on my lighter powered reloads, more so when the powder prefers being loaded hotter, so it burns dirtier.

Powder residue most likely...
 
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James K

Member In Memoriam
Blackening of the case at the front is due to the case not fully expanding to seal off the gas, so some leaks back around the case and causes the black marks.

That is often due to a light load which has not enough pressure to expand the case, but that is not too likely in an auto pistol where a certain amount of pressure is required to operate the pistol. But case expanision can also be prevented by dirt or grease in the chamber, or by a chamber that is a bit too large. If a cleaning doesn't help, and the condition persists, I would not worry about it. It won't interfere with functioning, and the worst that happens is that you will have to clean the brass when reloading.

Jim
 
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