Sooty case mouth 9mm

[Black Jaque Janaviac]

I've been using BE-86 for my 9mm and I seem to get sooty case mouths. Can this indicate a problem? Or should I not worry? I'm getting 2-3 inch groups @ 10yards with a subcompact. Velocities and acurracy seem to be comparable to what I get for factory lods. Except factory loads look cleaner on the outside.

[Hick]

I get sooty case mouths too-- but I'm using Titegroup in my 9mm. Several thousand rounds with no issues-- so I don't think it is indicative of a problem. I'll be watching other answers on this.

[onelight]

The soot does not hurt any thing and if you like the load keep shooting , but it can be a sign that the load maybe a little light , if you want to see if you can reduce it and you are not at max for your bullet move toward max at a tenth or 2 of a grain at a time and see if it cleans up.

[Winger Ed.]

In 9mm, I always used Unique, but I thought that soot was normal.

[Prcshooter]

I use clays and get very little soot but soot is pretty common

[kevin c]

I've read that it's a lack of obturation: the load's internal ballistics don't generate a sufficient pressure curve to fully expand and seal the case wall against the chamber, so once the bullet leaves the case mouth, the burning powder gases not only move forward to continue pushing the bullet, but can work backwards as well, making the case and chamber sooty.

I haven't heard that it's actually harmful, the main result being a dirty gun and sooty brass. If you don't like it, with a sub maximal load you can try a cautious increase in the charge, keeping all other load characteristics the same.

[hermans]

I've read that it's a lack of obturation: the load's internal ballistics don't generate a sufficient pressure curve to fully expand and seal the case wall against the chamber, so once the bullet leaves the case mouth, the burning powder gases not only move forward to continue pushing the bullet, but can work backwards as well, making the case and chamber sooty.

I haven't heard that it's actually harmful, the main result being a dirty gun and sooty brass. If you don't like it, with a sub maximal load you can try a cautious increase in the charge, keeping all other load characteristics the same.

Very interesting kevin c......I once shot a pistol match and there were two ladies from Germany in my detail just shooting for fun whilst they were on tour here in South Africa. They were using S&B 9mm ammo and they said that it was new "super clean" burning ammo. I picked up a few of their spent brass, and man was I amazed at what I saw!!
The brass looked like it just came out of a wet tumbler......shiny and clean inside and out.....so maybe the soot that we get from our 9mm reloads could be a combination of our primers and powder not being that "clean burning".........very interesting.
I am going to increase the powder charge in my pet load and see if the soot does get less.....but I also thought that it is normal with reloads, my vibratory tumbler removes the soot from the brass in no time.

[DHDeal]

I think that a couple good answers have been already been posted. When I begin a work up and am at a lower charge (safety you know) the cases will have more soot on them than when I get further "up" on charge weights. For my own thought process I consider it a pressure thing. When a powder is in it's zone, I'll usually see cleaner burn and better accuracy. HS6 is a good example here for me.

The good thing with a 9mm, a .2 grain increase will let you know. The bad thing with a 9mm, a .2 grain increase will let you know.

You didn't mention whether you were shooting jacketed or cast bullets. I think the assumption is you were shooting cast.

[wv109323]

The soot will not hurt anything. The brass case acts as a seal that should keep all combustion ( and pressure ) going down the barrel. The brass swells to form a tight seal and then contracts. Soot on the side of a case indicates some blow by. If it bothers you you can increase pressure ,more powder, or go to a powder that burns more efficient in the barrel length. Usually that is a quicker powder.

[Black Jaque Janaviac]

If the soot is not linked to a problem then I won't worry. I figured it was from gas blow-by (backwards). I also know that gas blowby in other areas is bad. It is bad for accuracy when it blows by bullets, and it can erode forcing cones on revolvers.