What's going on? Problem with 7.62 x 54r reloads

[aprayinbear]

What is going on?

I recently reloaded some 7.62 x 54r for target work with my MN. I was using winchester brass, standard large rifle primers and Hornady .3105" 174 gr FMJ/BT. I don't remember the exact dimensions of the bore when I slugged it several years ago, but as I recall it was approximately .312. I have used .313 lead bullets that I purchased with good success. I seated the bullets to the crimp groove. Powder was 43 grains Varget. Lee lists that as a starting load for 180 gr. jacketed bullets, so I figured I was safe.

Anyway, my accuracy was good, recoil was manageable, but look a what I found with several of the cases. Yuck! Don't know what caused this. Brass has probably been reloaded 4-5 times with light gallery loads prior with no noticeable signs of wear.
http://i50.photobucket.com/albums/f3...psf665c29d.jpg
After taking some fine steel wool to the brass this is what I was left with...
http://i50.photobucket.com/albums/f3...psa9486397.jpg
and this is what the primer looked like......
http://i50.photobucket.com/albums/f3...ps63b277cd.jpg

Once I cleaned the brass a bit I looked for cracks, etc, but could not feel any. The primer seems flattened a bit.

If you have any thoughts, please help. Of course I want to be safe.

Information

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[Buntlineguy]

Looks like residue from coated cases. Hot water and soap to clean out corrosives, and solvent with bore brush ( I used brush on long rod and drill at slow speed ) to clean lacquer- based coatings used on some surplus cases. Solved my problems.

Good shooting
B

[WarPig1976]

Looks like the case isn't sealing against the chamber wall and your getting blow by. Same thing happened to me except it was a K98. My advice is up your charge to somewhere in the middle of the load data you have and it will go away. This is assuming the chamber is in spec and clean...

[ptf18]

Ive slugged the 4 MN I have and wouldnt use anything smaller that .312" dia bullets in them. You might try a larger diameter bullet.

[jimb16]

I'll be you fired them without inspecting the cases first. That looks like typical brass corrosion to me. I've seen it on many cases in many calibers. If you run your fingernail over it, you can feel the roughness from the meatl being eaten away. Just give them a good cleaning and as long as the case isn't split, I'd go ahead and continue using them. You only need to be concerned if the corrosion is deep. If it is, then scrap the case.