Carbon Coated Cases

Could one of the smiths give me an idea what would cause one side of the spent cases to be covered with carbon. This happens with my both my reloads or factory ammo. I am reloading Zero 185 JHP/4.7gr 700X long line and Zero SWCHP/3.9gr BE short line. This happens with either load. I am using a 9.4# recoil spring. If I go to a 9.8#, the slide will not lock back. Both springs were tested on a spring tester from Brownells, so whether the poundage is accurate or not , I do not know, but they were tested on the same gauge as a reference. Here is what I am looking at:

What is your crimp?
Jon

Also what pistol/barrel?
Jon

oh, my, you mean that's not normal??

I wouldn't expect much from 4.7 gr load if crimped right. But if fat chambered then it'll do it.
Jon

james r chapman wrote:oh, my, you mean that's not normal??

Stop it......

Jon: Thanks for the reply. My crimp is .469 for JHP (top pic) and .467 for SWCHP (bottom pic). the frame and slide are both Caspian (not done by self) and a KKM barrel and accu-rails. As you can see, the SWCHP staining seems to be more pronounced than the JHP, but both are there. It might not be anything, but it just bugs me. None of my other 45s have this problem. It is almost like it is coming out of lock-up too soon. Paul

Well those are good crimps. If the gun is shooting accurately I wouldn't sweat it. All those are Quality Parts but we don't know what chamber reamer was used so we really don't know whether you have a fat chamber or not which could contribute.
Jon

Thanks Jon. The gun is shooting fine. Better than I am lately it seems, so I guess I won't worry about it anymore.

Neither a gunnie nor a BE shooter here. But could that be indicative of a out of round chamber. Just curious?
The chamber in my Bar-Sto barrel Hoag was about .0015 out of round and I could see it after cleaning the chamber. The chamber was somewhat discolored in he area of the O/R condition.

No Gary. Common for one side to get the soot. But if chamber was larger diameter it can get more blow by.
Jon

Many thanks for the clarification, Jon. I always wondered.

james r chapman wrote:oh, my, you mean that's not normal??

+1

If I didn't know better i would say you picked up my brass.  Don

Mine are always like that. Never gave it much thought. The loads we use don't make enough pressure to expand the brass and make a seal to the chamber, so you get some blow by.

A "carbon" copy of fired cases from my 9mm mostly-stock RO and 986 revolver.  Both shoot well and I've stopped looking at it.  My 986-spent cases have so much soot on one side I have to rub them in a cloth with Rem-oil before decapping/sizing to reduce the friction.  The 1911 Forum has many posts regarding this issue.

Multiracer wrote:

james r chapman wrote:oh, my, you mean that's not normal??

Stop it......

lol

I get it too with light loads I get a little less with WST then BE. Is the inside of the case black? If the inside of the case has carbon watch out that means the powder is burning.....