black soot on neck and shoulder what does it mean

[clem81]

i have a new 243AI 1-8 benchmark 26 in barrel i have fireformed 25 cases and after reloading 2 times i am am still getting real black sooty necks and shoulders. i am reloading 44-45gr h4350 and 85 seirra HPBT.
what does the soot mean.

craig

 

[fdshuster]

craig: That's carbon fouling you're seeing. Normal by product of the burning powder, and the same carbon deposits are in the bore. If left unattended will become a problem somewhere down the line in the form of higher pressures.

Some powders are dirtier than others, most ball powders being the worst.

If you are willing to take the time, it is easily removed from the case necks immediately after firing by wiping off using a rag dampened with plain old Hoppe's solvent. The longer you leave it on the case necks, the more difficult it is to remove.

I am particular about keeping the case necks clean and remove the carbon before running them into the bushing sizing dies. I do believe the carbon is hard enough to damage the inside of the bushing or neck area of a standard sizer.

 

[chevytruck_83]

layman's Turbo Polish on a rag works wonders as well. from my experience tumbling with it mixed in the media. the fouling doesn't stick as much. I read somewhere that a properly built tight tolerence benchrest gun will not do this when brass is sized properly. I would guess that he neck is so close to the chamber size that when fired it seals upon firing.

 

[seattleray]

My .243 Ackley arrived, think I will neck turn a few fire formed cases to see if carbon ring reduces........r in w.

 

[Klong]

May be time to anneal brass.

 

[areaone]

Would the carbon on the neck and shoulder be from the blowback of carbon because the neck is not sealing the chamber upon expansion? Low pressure not expanding the neck enough to chamber dimensions? I have the same problem when I use 85 gr bergers in a 6.5x47L, I even get carbon on the case almost down to the web, can not figure out why this is happening. Any Ideas?????

 

[bheadboy]

This is a problem often when slowe powders at low or medium pressure loading are failing to seal the case to the chamber prior to the bullet exiting. increase the load or go to a faster powder.

Bob

 

[SixDasher]

Dito on the faster powder or higher load. I have the same on my 220Begs using N133 and 52gr bullets. When I stick in a 60gr bullet with the same 24.8gr load, the case seals up (more pressure ofcourse due to heavier bullet). I don't have the black cases when I use N130, even with the lighter bullets and mild loads.

Do clean the chamber and bolt when you get black cases back to the web! It builds up quickly.

 

[savagedasher]

Could be the neck size of the chamber check a fired case and a sized case.that should tell you how much it is expanding. Good Shooting Larry

 

[25AI260]

45grs of h4350 is close to a max load in a .243 ... a 243AI should be able to take ? maybe ? 2 or 3 grains more powder ... sound like pressure may be low....

guess'n

 

[bigedp51]

clem81

On almost all my rifles I start at the suggested starting load and work up to maximum. At low pressures you will get soot around the body and neck of the case and you will have the primer backing out of the primer pocket. My 30-30 at 38,000 cup chamber pressure will always have soot on the neck. This will vary depending on how new your cases are and the softness of the upper 1/3 of the case.

Many times in this forum I have read that some shooters will keep increasing the load until the ejector hole in the bolt face leaves a mark and then they back off a few grains. Others will measure base expansion as a sign of over pressure. The is why load information varies between loading manuals and different rifles.

Read the link below in the .243AI loading section for some reference.

http://www.accurateshooter.com/cartridge-guides/243win/