P238 Powder burns on shot shells

September 24, 2019, 01:13 PM

samual58

After firing a new P238 I noticed the spent shells had black powder burns covering one side of the casing about halfway down the length of the shell. Is this normal? I called Sig customer service and they acted like I was wasting their time. Are large powder burns on the outside of spent casings normal and was I indeed wasting their time? Thanks

September 24, 2019, 01:28 PM

sigfreund

By “shot” shells I thought you were referring to cartridges loaded with birdshot, so I’m glad I looked in.

I wouldn’t usually call black marks on a fired cartridge “powder burns” but rather firing residues of the same sort that end up in the barrel and on other parts of the gun. The presence of fired powder residues on cartridge cases is hardly unusual; it’s common in fact. If the residues are unusually heavy, though, it may indicate that the case didn’t expand as quickly or as fully as other cases might, thereby allowing powder gas to flow back between the case and the chamber wall. That can have a couple of likely causes. One is that the case itself is resistant to expanding and sealing the chamber because the metal is thicker or stronger than usual. The other, and probably more common reason is that the load is low powered.

I doubt I would be worried about the phenomenon, but if you can post photos of the cases for us to look at, we would have a better idea if the residues are unusually heavy.

As a side note, the HK P7 pistol has flutes in the chamber that are specifically intended to permit gas to flow between the chamber wall and the cartridge case to enhance extraction.

Welcome to the forum.

September 24, 2019, 01:53 PM

AZSigs

Occurs depending on powder manufacturers choose. UMC is the worst for powder residue on the brass casing. It's not a clean burning powder they use.

September 24, 2019, 01:57 PM

sns3guppy

When there is insufficient chamber pressure to expand the brass during firing, the gas flow will leave deposits in some chambers on the brass where the gas escapes aft past the chamber mouth.

It's very common on downloaded "low recoil" loadings to make minimum power factor for some competition rounds.

With pistol shot, there's little chamber pressure to start with, little resistance, and the brass or aluminum isn't expanding much, if at all. You're seeing evidence of gas flow past the lip of the case, aft through the chamber.

September 24, 2019, 01:58 PM

parabellum

Nothing to worry about at all.

September 24, 2019, 02:05 PM

Stroonz

It's more a problem of the cartridge and not the gun. Usually that occurs when a slow burning powder is used with a light bullet....if you were a reloader I'd advise you to switch to a faster burning powder.

The 238 is a wonderful hand gun and what I carry on and off with my Glock 42.

September 24, 2019, 02:41 PM

samual58

Thanks for all of your thoughts. Firing residue is the term I should have used. All responses make perfect sense. I was using Sig Sauer Elite performance ammo at the time. I tried posting pictures of the spent cartridges, but I was highly unsuccessful.

September 24, 2019, 02:55 PM

samual58

Firing residue would be better description. I would not say it was heavy residue. It was Sig Elite perf. ammo I was using. I tried posting pictures but failed miserably. Thanks for great explanations.

quote:
Originally posted by sigfreund:
By “shot” shells I thought you were referring to cartridges loaded with birdshot, so I’m glad I looked in.

I wouldn’t usually call black marks on a fired cartridge “powder burns” but rather firing residues of the same sort that end up in the barrel and on other parts of the gun. The presence of fired powder residues on cartridge cases is hardly unusual; it’s common in fact. If the residues are unusually heavy, though, it may indicate that the case didn’t expand as quickly or as fully as other cases might, thereby allowing powder gas to flow back between the case and the chamber wall. That can have a couple of likely causes. One is that the case itself is resistant to expanding and sealing the chamber because the metal is thicker or stronger than usual. The other, and probably more common reason is that the load is low powered.

I doubt I would be worried about the phenomenon, but if you can post photos of the cases for us to look at, we would have a better idea if the residues are unusually heavy.

As a side note, the HK P7 pistol has flutes in the chamber that are specifically intended to permit gas to flow between the chamber wall and the cartridge case to enhance extraction.

Welcome to the forum.