A question about shot casings

[MrplVan]

Hi everyone,

Finally, I can include images in my posts. YAY!

Just wanted to show my Ruger PC Carbine to the community, as well as ask a question.
When shooting at the range I notice that my used casings have well visible traces of burns (carbon deposits) around the rims as well as on the walls sometimes as far as half way down their height. I saw other used casings on the range, and they looked mostly brass shiny with almost no black stuff on them. I am wondering if it is normal for this type of firearms and ammo.

 

[joemanco]

Black is inefficiently burned hydrocarbon. Very normal for a straight blowback PCC because the bolt is moving back before the bullet exists the barrel.
The shinier cases may have come from handguns - because a tilting barrel is a (momentary) locked breech, so more complete combustion.

 

[DiMP]

Normal. Straight wall cases (like your pistol rounds there) don't expand to seal the chamber as effectively as bottleneck cartridges. Depending on how tight your chamber is will change the amount of soot you'll see on the cases which is why your range buddy's cases may not look the same. Even different brands will expand differently and/or use different powder that will burn cleaner or dirtier

 

[legi0n]

try some winchester winclean ammo if you can find any

 

[Butcherbill]

Normal like already said for a blowback, or depending on how much room the chamber has.

You’ll see this with straight walled cases also when hand loading and working up from a starting load, you’ll hit a certain powder charge and things will clean up as the case fully expands in the chamber. As pressure increases the gasses and fouling can’t sneak around the mouth as much, spent cases are cleaner and there’s less fowling in the action.

 

[MrplVan]

Thank you very much everyone! That makes perfect sense.

 

[quinnbrian]

Yes and they get dirt quickly...just like a semi 22 rimfire...I shoot my reloads( JR 9mm) and I get 4-5..7 reloads on my cases, only had couple head separation, because of how many times they've been reloaded....