What causes this carbon fouling?

[rutilate]

My son shot some fresh reloads at the range and many of them were carbon fouled on one side like in the picture below. What would cause something like this? The loads were underpowered and wouldn't cycle the action. He also said that he felt something very small hitting his face like shrapnel.

Is it possible that the load was so underpowered that it could hardly propel the round out and so blew backwards?

I seated and just barely kissed the case mouth with the crimping die to remove the bell. I'm using Berry's 185 gr HBRN, Titegroup at 5.1 grains.

 

[jasons]

I'm going to guess not enough crimp. If you crimp them a bit more do you see the same issue?

 

[EddieCoyle]

Underpowered loads will do that. See if they clear up when you load them hot enough to run the gun.

 

[Supermoto]

Underpowered loads will do that. See if they clear up when you load them hot enough to run the gun.

This

 

[rutilate]

I'm going to load up a few more tomorrow and see if I can find a better powder level. Thanks for the feedback.

 

[gerrycaruso]

5.1 of Titegroup with a 185 grain bullet is very light. If I remember correctly, I loaded 6.2 with that weight. I'm guessing EC is correct. There's probably not enough pressure to expand the case against the chamber.

 

[SJan]

5.1 of Titegroup with a 185 grain bullet is very light.

He is using a Berry's 185 gr HBRN. Hollow Base Round Nose. These bullets leave more case volume when loaded to the same OAL of a 230g round nose. For that reason you can't rely on data for any other 185g or 230g bullet. The powder level that will work best will be somewhere between the listed loads for both

 

[formula]

I see the same thing in my light .40 loads, although not as sooty as your picture. 180gr Missouri TCFP, 4.5gr W231, CCI500, 1.135 OAL. After a few hundred rounds I clean the gun. All good. (or not, it's a .40)

ETA: With hotter loads there is little to no soot on the sides.

 

[Gammon]

Soot on the outside of the brass is caused by a load that is too light to expand the case to seal the chamber, so some gas and soot get between the case and chamber wall. This could also account for the matter striking your son's face as the gas and soot can continue to the rear (along the slide rails, for example) and hit the shooter.