Soot around case mouth

[DonMountain]

I just fired some 8mm Mauser loads with a newly purchased LEE Karibiner gas checked bullet of about 235 grains, and 25.0 grains of IMR-4198 and Winchester WLR primers. The cases show no pressure signs on the primers. But I am getting black soot just around the outside of the case mouth above the sholder. Is this load not sealing the case mouth against the chamber wall properly? Do I need to increase the powder load weight? I got good groups with the load, 5" at 100 yards using the factory open sights, which is about all I can hold or see.

[oneokie]

Could be from a low pressure load or from work hardened case necks. How many times has this brass been loaded?

[Sonnypie]

It's the light charge, and possibly hardened cases.
I was experimenting with reduced loads trying for some the Grandson might be enticed into shooting in the 30-06.
I managed to get into the downright comical end of shooting. 15g of IMR 4895 is a BLOOP load. Because that was what it sounded like, BLOOP.
And the reduced loads were "sooty".
Try crawling up in your load, more pressure will get a better seal.

[ku4hx]

I just fired some 8mm Mauser loads with a newly purchased LEE Karibiner gas checked bullet of about 235 grains, and 25.0 grains of IMR-4198 and Winchester WLR primers. The cases show no pressure signs on the primers. But I am getting black soot just around the outside of the case mouth above the sholder. Is this load not sealing the case mouth against the chamber wall properly? Do I need to increase the powder load weight? I got good groups with the load, 5" at 100 yards using the factory open sights, which is about all I can hold or see.

Low pressure load. Insufficient pressure to expand the case and effectively seal it to the chamber.

[Larry Gibson]

As mentioned; too light a charge with not enough psi to seal the case mouth. 4198 is probably not the best powder for that heavy a cast bullet in the 8x57. I would suggest a medium powder such as RL7, 3031, 4895, 4064 or Varget with a dacron filler. Or a slow burning powder such as RL19, AA4350, H4831SC or even RL22 with a dacron filler if loading density is 80% or less. You'll probably want to push that bullet to 1800 - 1900 fps for best accuracy.

Larry Gibson

[DonMountain]

Could be from a low pressure load or from work hardened case necks. How many times has this brass been loaded?

Once. These were new cases and I only fired this load in them for the first time. I will try some slower powders than IMR-4198 as suggested. How are others avoiding this issue with the really fast powders like the most "popular" loads of Unique?

[ku4hx]

Once. These were new cases and I only fired this load in them for the first time. I will try some slower powders than IMR-4198 as suggested. How are others avoiding this issue with the really fast powders like the most "popular" loads of Unique?

3031 did it for me in my .30-'06.

[runfiverun]

it isn't anything to worry about.
your chamber has larger necks.big deal.
you could clean things up by going to 50k-55 k in pressure, but i doubt the accuracy will improve.
soot is a lubricant on brass anyways.
if you want to help eliminate it just don't size the necks all the way down, this will help align the cases with the bbl too.

[Certaindeaf]

This works good.

http://members.shaw.ca/cronhelm/TheLoad.html

[rexherring]

I had that on some reloads with reduced loads and over used cases. I did anneal the case neck shoulder area again and it stopped.

[runfiverun]

it's an 8 mauser and i doubt it's a remington.
i'm pretty sure the neck is big.

[44man]

Remember that case pressure goes down quick even thought it is still pushing a boolit. Carbon and lube can get on the outside of brass. Pressure is reduced the farther the boolit is from the brass. Brass does not stay at chamber walls for the duration.

[DonMountain]

I tried heavier loads of the IMR-4198, up to 29 grains, but still didn't eliminate the soot around the outside of the case mouth. So I switched to 35 grains of IMR-4895, and that did the trick and still maintained my accuracy. A 4" group at 100 yards centered just 2" over the center. So I went up to 38.0 grains of IMR-4895 and the cases were as clean as when I put them in the rifle. And the primers showed no pressure signs. And the chronograph showed really close velocities of all five shots I fired. But only one bullet hit the target. About 14 inches high. I assume that the rest of them went over the target. But no leading shows in the barrel. I will try another set of this load and sight lower on the target to see what happened. The rifle is a converted Turkey GEW 88 with a 100 meter lower setting on the sights. When cast boolits strip the barrel do they usually show inconsistant velocities too?

[Larry Gibson]

I believe you will be well beyond the pressure limits of the 8x57 before you "strip" a cast bullet that heavy.

Try backing down to 28 gr with the 4895 and use a 1/2 - 3/4 gr dacron filler. Work back up until accuracy goes south or you are at 36 - 38 gr. You might find a more accurate and efficient load in there.

Larry Gibson

[DonMountain]

I went to the store to look for "Dacron Filler" but nobody there knew what "Dacron" was. Is that some sort of stuff they used to use in pillows a long time ago and everybody still has a bunch left over from the dark ages before everything was made out of plastic? Or is it polyester fill like they sell for pillows and the elderly ladies at church make those thick blankets with designs all over them for church sales?

[runfiverun]

yep quilt batting.
roll it out and cut it into squares.
i use the loose pillow fill stranded stuff, mainly because i got a big bag of it at a yard sale for a quarter.
the fluffy filling in most stuffed animals works too.