curious scorching on brass

H

HighValleyRanch

New member
Shooting out a Kahr P45 with a Lothar Walther match barrel.
I noticed after shooting new factory brass, that each casing has a blackish scorch mark on one side of the brass. Just curious what is causing that?
What's you opinion?

Functions perfectly, and accurate. But cursious when in the timing would there be opportunity for the case to get scorch and how, since it's in the chamber at the time of the powder being burned.
 
Do you mean soot? Most common cause of that is incomplete obturation. Are the rounds a little on the low power side? It doesn't worry me when I see it.
 
So is it because the case does not expand fast enough to fit the chamber before the power burns?
Click to expand...

I believe so, and that less than max pressure is developed to make the brass flow as much as it normally would. I usually see this in my lighter reloads (when my Lee auto disk doesn't have the optimum choice) and in steel casings which are a little stiffer.

If it's practice ammo, I think the soot would stop if it were loaded a little hotter. Maybe try a couple premium rounds and see. My cases never come out completely sparkly though, it might be the fast powder burn rate and short barrels I've been shooting the past few years. You could try your PMC rounds in a longer barrel and see if the extra length allows for a cleaner or more complete burn.

I'm guessing it's not the barrel/chamber unless there are nasty machining marks everywhere. But it's a Lothar Walther so probably not.
 
Or, it may be due to the power used.

I have used CFEpistol for a few years, and it will cause a blackish residue on the outside of 9mm cases. And, I am over the maximum grains that Hodgdon recommends.
 
I remember from my bullseye days that bullseye and unique powders were pretty dirty.
I was just wondering, though why it was just on one side of the case. There was no way to determine if it's always the same side, but they all look pretty identical, instead of radom sooting. Made we wonder if the chamber was oblong somehow? The chamber is fully supported and the sooting is on the bullet end, not the rim end.
 
I had originally typed about your casings or chamber being out of round but then deleted it because I thought that properly fire formed brass would cover that problem. After all, 40 cal brass that has been Glock'd swells up significantly.

There was no way to determine if it's always the same side, but they all look pretty identical,
Click to expand...

There is a way. I've seen someone do this on YouTube on precision AR reloads (6.5 Creedmoor I think?) to make sure that oblong cases or deviated bullets were always loaded pointing the same direction in the chamber. To make up for imperfections in the reloading process. He measured things first, you wouldn't have to do that, just draw a line.

You could draw a black Sharpie line up one side of the brass and load it into your mag so the line is pointing up. Do this for all the rounds and load your mag so all the lines are at the top. Then you'd have a landmark to see where the soot occurs relative to the top of the case. I don't think the cases will rotate much on just chambering.
 
So is it because the case does not expand fast enough to fit the chamber before the power burns?
Click to expand...

this is possible. There is a second possibility, and that is, things are working normally.

Yes, the soot is from powder gas getting between the case and the chamber wall, and this CAN happen before the case seals to the chamber.

BUT, it can ALSO happen when the case "unseals" (springs back) as the pressure drops. powder gas is still there, and can mark the case before the extractor pulls it out of the chamber. This is normal. Some powders simply are much dirtier about it than others.
 
Sounds like lo power loads. Carefully llad mag pr i tp chamber with same headstamp orientation to see the mark.
 
I had exactly the same issue with a Browning 1911-380 Auto. I using 3.2gr (max)of Titegroup with a Hornady 90gr XTP HP. The cases were tarnished solid black around one-half of the case. One of the references suggested seating at 0.980" which I did. I found another that recommended 0.955". I seated the bullets deeper and resolved the problem.
 
"...case does not expand fast enough..." Isn't about how fast. It's about expanding at all or incompletely.
That .980" is likely the issue. The MAX OAL for the .380 is .984".
 
" The MAX OAL for the .380 is .984".

It must depend on the gun. The Hodgdon site for .380 Auto lists COL at 0.970" for a 90gr HDY JHP with CFE Pistol, but with HP-38 and TiteGroup, the same bullet is seated at 0.955".

The difference is the powder and pressure I suppose but my pistol did not function with Titegroup at 0.980. Maybe it would at 0.970, but it sure does at 0.955"
 
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