Necks are .248 loaded and chamber is supposedly .251. I'm getting blowback down past the neck shoulder junction onto about 1/16" the shoulder of the case before it seals off. If I use a bushing die I don't see it as often as a fl die used in conjunction with an expander but accuracy is not as good with the bushing die. I loaded 30 up with the bushing die yesterday and fired 3 strings of 10 at 600 at a F class target and the shots that dropped low were ones that didn't seal at the case neck and soot ended up on the shoulder, those shots were slower across the chronograph as well. How much damage is it doing to the chamber when cases are not sealing completely on the neck and with a low powder capacity cartridge case (24 gr) is it ok to run tighter neck clearances than you would with 2x the case capacity?
Soot on Case Shoulder
- Thread starter jsthntn247
- Start date
My thoughts also. Larry
I anneal after every firing. There's plenty of powder as I generally on get 3-4 firings on the brass before the pockets get loose, that's the main thing that's got me confused. When using H4895 I got blow by every time whether it was a bushing or fl die. With Varget it's only 1 or 2 out of 10 with the bushing die even though the loads are running within 10 fps of the same speed of the 4895 load.
The reason for then soot being on the neck it is not sealing carbon rings can do that also .
Larry
Soot on the shoulder; I am not the fan of soot on the neck and or the shoulder. For me it is a matter of time, I want my case to expand to seal the chamber, when I get soot on the shoulder things are not happening fast enough. Then there are reasons, there is a chance the bullet is not large enough to seal the barrel, there is a chance the diameter of the barrel is too large in diameter for the bullet and then there are slow powders etc..
F. Guffey
F. Guffey
+1 slow and sooty. Not enough pressure to seal the neck.
"Trust, but verify." R. Reagan
Not sure Mike, I trim to .005 over saami
Is it headspace correctly. A friend of mine had that problem. We measured case from base to datum line on new and then on fired and found .017 to .021 difference. The reset barrel, problem solved
The 'sooty brass' phenomenon was prevalent with the various WSSM cases I've messed with over the years. WSSM brass was so dang thick, they'd soot right up bad if too slow a powder, or too low a charge was used...
Agree with above, if the chamber's cut correct & you're not oversizing brass, annealing and/or upping the powder charge, or switching to a faster burn rate should help.
Good luck!
Agree with above, if the chamber's cut correct & you're not oversizing brass, annealing and/or upping the powder charge, or switching to a faster burn rate should help.
Good luck!
I have a rifle with that type of chamber, it is .016" longer than a minimum length/full length sized casa. The kind people that manufactured my press and dies furnished both with threads. Because my cases do not have head space I off set the length of the chamber with the length of the case. When forming/sizing I add .014" to the length of the cases between the shoulder and case head. The added length of the case give me the magic .002" clearence.
F. Guffey
Your bullet is exiting the brass before the brass expands enough to seal the chamber. As stated several times before, work hardened brass and/or chambers a little larger than the sized brass can do this. Hotter primer or a little hotter load can sometimes be the cure if annealing doesn't work.
What I have found to be the biggest draw back, in addition to dirty cases, is the dirty chamber. You have that soot and crud building up in your chamber too. I have a couple of guns that are right on the fine line like yours. Eight shots will be fine then one will soot up the brass. Quick touch with a chamber mop helps keep down any build up in the chamber.
Thought I would share what little I know on the subject....
Steve
What I have found to be the biggest draw back, in addition to dirty cases, is the dirty chamber. You have that soot and crud building up in your chamber too. I have a couple of guns that are right on the fine line like yours. Eight shots will be fine then one will soot up the brass. Quick touch with a chamber mop helps keep down any build up in the chamber.
Thought I would share what little I know on the subject....
Steve
You gotta know this is meaningless to your end clearance, and another potential contributor.
With bigger neck clearance and slower pressure peak, a bullet is fully released greater time before neck sealing. Add bigger chamber end clearance and gas at pressure has a shallow/easy angle to slip back past the neck -slowing neck sealing time further, and adding to ES.
I'll add that I shoot a 6.5wssm with fitted necks(turned to 1thou total clearance) and 5thou end clearance. Zero sooting, no need to wipe any necks clean, ES <8fps. Not bad for a dreaded wssm I guess. You can get there to.
I had this exact problem with a 300 wsm and I found that I was bumping the shoulder back way too far. I don't know if this is your problem but it is easy to check.
Two items to consider one being a weak FP spring and possibly bad primers,,,not a powder mix up ?
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