Sooty cases

Status
Not open for further replies.

DLrocket89

Member
Joined
Dec 29, 2012
Messages
242
Did my first reloading for a bolt rifle in 10 years, shot it yesterday. Savage Axis Compact, 243 Win. I noticed that the OD of the necks are really sooty but the rest of the case is pretty much pristine yet. Is this telling me anything positive or negative? I haven't reloaded much for rifle, not really sure if I should be worried or happy about this:

IMG_20170218_171801488.jpg
 
Soot just means you didn't have enough pressure on that particular load to expand the case mouth fully. If you are terribly worried about it you can work your charge up safely.

Honestly though if you were able to put the bullets where you wanted on the target don't worry about the soot.
 
I've seen similar with pistol rounds, but this 243 was kicking like a 308 and was afraid I was overpressuring something somehow. 3000fps on a 95 grain bullet from a 20" barrel.
 
If it was over pressure the cases would have zero soot on them among other things.
As long as you are within published limits and assuming a good firearm you should be fine.
Is there anything else wrong with the cases? If not, then shoot them.
 
Think of it this way. That cartridge sealed as you can see by the straight line at the back of the neck where the taper of the bottleneck starts going backwards toward the case head. That part of the case expanded and reached the chamber sealing up before the case mouth did. That's why the line is where it is.
 
Case necks rarely, if ever, press against chamber necks. Little pressure on chamber necks because bullets are several inches down the bore at peak pressure. Pressure is about equal on the outside and inside on the case neck. Powder residue easily gets on the outside of the case neck. Rarely do fired bottleneck cases have no powder residue on them. The opposite is true for case bodies; they rarely have powder residue. Cases seal to the chamber starting at the shoulder then work back as pressure increases.

Transducer pistons measuring psi are a ways back of the shoulder because of pressure at the case neck transferred to the barrel is not the same as in the case behind the shoulder. It takes much less pressure to push case bodies against the chamber than the case necks against the chamber.
 
there is enough pressure generated by a 243 win load to press every part of the case against the chamber wall.

the carbon gets between the case neck and chamber wall when the lateral pressure (no matter the amount) equalizes on both sides of the case mouth and allows the case mouth to "spring back" a thousandth and allow the carbon to travel to the outside of the neck.

the rest of the case is immune to this because the pressure on the shoulder of the case pushes the case shoulder against the chamber at an angle to the bore creating an axial (front/back) pressure on the shoulder. so, the pressure pushes forward on the shoulder and rearward on the breachface (bolt) keeping the carbon out of that part of the chamber.

the case neck is free to spring back almost immediately and lets the carbon soot flow around the mouth to the outside of the case neck. this happens all the time so, no worries.

murf
 
Interesting thread DLrocket89
I'm fairly new to reloading (almost a year) and noticed my 270 cases looked just like yours. Never thought much of it since I can shoot .75" groups at 100 yds and cases last about 6 reloads. Rest of the case stays clean and no signs of over pressure.
 
Mine always did this. I think Bart and Murf are both correct. Both things happen.
Little PSI is at the case neck. They may well get pushed out some but would spring back exactly when that bullet was released. That would allow soot on the neck. But, Bart is correct about where the PSI is mostly.
1/2" to 3/4" groups at 100 yards is what I always saw from my .270s.
 
Some fired factory brass for comparison.
index.php
 
Status
Not open for further replies.
Back
Top