Soot on Fired Cases?

[Mikee Loxxer]

I have recently loaded a number of 7.5 MAS (7.5 X 54) cartridges using a Hornady 130 grain soft point bullet over 48.4 grains of H414 which is 1.43% below the do not exceed load listed in the Lee reloading manual. The primers being used are Winchester Large Rifle primers. The cases are FNM, Prvi Partisan, and Graf and Sons.

Yesterday I went to the range and tested this load in my MAS 36. I was pleased with the ballistics as the point of impact at 100 yards was approximately 2 inches above the bullseye with the rear sight at the 200 meter position. In the past when using both factory FNM ammo and some of my lower powered handloads I had to move the rear site to the 600 or 800 meter position to achieve a 100 yard zero.

What I noticed about the cases is that they were covered with a black soot like substance after being fired. The bolt opened easily and the primers did not show any evidence of being blown out the back of the case. What does the presence of this black soot like material on the fired cases mean? Is this a sign of excessive pressure or something else I should be cautious of?

 

[Ben Shepherd]

Soot heavier towards the case mouth, tapering off towards the case head? NOT soot leaching around the primer? Sounds like a low pressure condition(case not sealing the chamber).

More likely however:

Use a dedicated magnum primer. Start with a federal large rifle magnum primer. IIRC it's a #215. Most likely that powder's having a hard time burning.

One thing: Make sure you back the load down and start over when you change primers. Especially where you're that near the top of the book.

 

[dfaugh]

Sounds like a low pressure condition(case not sealing the chamber

).

Ran into the same thing when using some "light" handloads in 8x57 Mauser("soot on top 1/2 of cartridge). Pressures (apparently) weren't high enough to expand/seal case to the chamber. We put a light crimp on (which raised pressures) and solved problem. Although in this case we never did get good accuracy until we switched bullets.

 

[Mikee Loxxer]

Correct, it is soot coming from around the case mouth and leaching all the way back to the case head. It is not coming from the primer pocket. The case must not be sealing properly in the chamber. I just can't see how this could be happening with the load being so close to the do not exceed velocity.Is this a dangerous condition? How would using a Magnum primer alleviate this?

 

[ocabj]

Are you neck sizing? That could help reduce case sooting since you'll get a better seal with the shoulder and chamber.

It's not a dangerous condition, perse. It could indicate excessive headspace if you are experiencing this with factory loads. But since you are handloading, neck sizing, as mentioned, will alleviate the issue. I get sooty brass in a few of my rifles with certain loads.

For example, in my 200 and 300 yard service rifle load using 77gr SMKs, the brass will soot. But with my 600 yard service rifle load using 80gr SMKs (in the same rifle), the brass will not soot.

 

[USSR]

Mike,

The soot you are seeing is the result of low pressure, as previously noted. H414, being a ball powder, should be set off with a magnum primer. Would suggest switching to a magnum primer and working your way up in regards to powder charge, until the soot goes away or you see high pressure signs on your brass.

Don

 

[Mikee Loxxer]

I am using a full length resizing die, I assumed that this resized the neck as well as the rest of the case. I did trim the cases after resizing, is that the correct sequence?

 

[Ben Shepherd]

Correct sequence. HIGHLY reccomend switching over to a magnum primer, and starting load development over.

Sounds like a low pressure condition caused by incomplete powder ignition. So, as posted above:

1. You can try a crimp if you aren't already. But I would still be leary of that load in cold temps. In an extreme case you could end up with a bullet and a pile of half burned powder in the barrel.

2. Switch to a magnum primer, start over on the powder charge weight, and I'm about 95% sure your problem will go away.

 

[Mikee Loxxer]

Thanks for the informative replies! I learned something today.

 

[Ben Shepherd]

Mikee, please let us know what you do to correct this.

If it isn't what I thought, I want to know what it was, so I can be on the lookout myself.