Carbon Around the case

[areaone]

I have never had this happen in the past 40 years of reloading. I am shooting 85 gr Berger, 6.5x47L using 39.3 grains of RL15 and getting carbon on the case and around the outside of the case around the web area. my FB is .123, so my bullets are jumping a lot since the 85 gr is a rather sort bearing surface. I used VV135 and have the same results, along with Varget. Any ideas would be appreciated, I think I have a clue as to what is may be, but want some confirmation. Any load information for these 85 gr would be also appreciated. Do I need faster burning powder?

 

[jonbearman]

Sounds like you are not sealing the breach caused usually by light loads. I would like to see a picture of the primer and shoulder area.

 

[areaone]

My thoughts exactly, no signs of pressure, yes, there is carbon around the neck and shoulder but not carbon around the primer. So do I go to a faster powder? I am thinking of 8208 as a alternative.

 

[Shynloco]

Sounds like you are not sealing the breach caused usually by light loads. I would like to see a picture of the primer and shoulder area.

I agree with jonbearman 100%. As I've been told, gases are forcing the carbon around the neck of the casing as it is not expaning completely and sealing off the chamber. I suspect that is the reason why the serious competitor have "tight chambers" (w/custom matching reamers and dies) to make sure all the pressure is expended on the bullet's forward movement and that pressure is consistent and there's no blowback such as in many other rifles. I get the same carbon deposits on most of my casings which is why I maintain a healthy supply of steelwool to clean it off. Hence I seriously doubt the burn rate of powder has anything to do with that carbon deposit, although "light loads" could contribute to the issue by not providing sufficent pressure for full and complete expansion the the casing to seal the chamber. Just my thoughts.

 

[260Ravage]

I had the same bad scenario with my .308. I loaded it a bit hotter and the problem went away. The light load,tho, was NOT the problem. The problem was simple. The cases simply needed annealing. They were no longer resilient. After I annealed the cases, my favorite light loads worked well and the brass,once again, sealed the chamber.

 

[swglenn]

How may times have you reloaded your brass? Like 260Ravage I found that annealing reduced the work hardening and allowed better sealing.

 

[areaone]

new cases or once or twice loaded

 

[LongRanger]

Have had same issue with 7 RM a coupla times. Once, the blowback was so severe it shoved the shoulder back .025. Blackened case all way to extractor groove. I found the following corrective measures worked individually....

More of the same powder.

A faster powder.

Increasing the neck tension.

The increased neck tension was a Big Bingo.....ES and group sizes shrank considerably.

Frank B.

 

[243winxb]

The Collapsed Shoulder is in an old Speer manual. Light loads & slow powder are the cause. Use a faster burn rate of powder. Pressure is low & neck not expanding to seal. Make sure the bullets have enough neck tension. The expander (if using one) should be .002" smaller than bullet diameter. This will keep the bullet from moving when the primer fires. The bullets bearing surface should be in full contact with the neck. If seating the bullet long to get close to the lands/rifling there may not be enough shank of the bullet in the case neck.

 

[areaone]

Well the jury is still out on all the suggestions, but I have tried two loads, 38.3 IMR8208 with neck tension increased and bullet seated as deep into the neck as possible, also with 39.3 RL15 same as described, both showed no carbon. Only shot these in the backyard into a stump, will try these tomorrow over a chrony with speed, es and grouping information to be noted here in a day or two. Thanks for everyones ideas, This site is invaluable for the information and experience that everyone is willing to share with "strangers". Thanks again, oh yes, I called Sierra-they could not help at all, very cordial, just no loading info for their 85 gr, and 6.5x47L. As long as the 6.5x47L has been available what is the problem with the bullet makers that they have no information on the cartridge. Thanks again to all.