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Thread: Black cases

  1. #1

    Black cases

    Can anyone suggest why I am getting this problem.

    I have a second hand Sako 75 in 6.5x55 which has performed flawlessly to date. A couple of weeks ago when out stalking I picked up a spent case and noticed it was covered in black soot. Later I fired two more which also came out black and one had pushed the primer out and had pressure marks on the back of the case. I stopped shooting and didn't fire any more rounds that day. The rounds I had were all from a batch that had been fine up till that point.
    I cleaned the rifle once home and tried some more rounds only for it to happen again. I then changed the rounds to a different load from 120 grain projectile to both 85 and 129 grain projectiles, neither of these produced black cases. So I swapped to use the 129 grain loads and had no problem next time I went out. Since then while zeroing the 85 grain loads have started producing black cases and then yesterday when stalking the 129 grain loads did also but only on the first shot which was through a clean barrel then it didn't do it again firing another three shots that day.
    I've asked several people about this and nothing seems to make sense. The loads are all no where near hot loads, they all use different powders and I've had no other pressure signs like flattened primers or stiff bolt lift. Any help would be really appreciated as I'm starting to get really pissed off with it.
    Many thanks.

  2. #2
    Sooty cases are caused by poor case obturation which in many scenarios is caused by Lee collet dies not sizing the case necks down sufficiently to give enough neck tension on the bullet.

    Ian.

  3. #3
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    Backed out, rather than totally blown out of the pocket, primers can be a sign of low pressure. How it works is that initially in all cartridges the primer starts to back out. Then as pressure increases the bullet and the case start to move. The bullet down the barrel and the case as far as the front face of the bolt. Effectively re-seating the primer.

    So that when you extract the case it will seem as if the primer hasn't moved and is still where it was seated. If you don't believe this fire a primed but otherwise empty case with neither bullet nor powder in it. You will get a case with a backed out primer. Although it might give you extraction problems! For which therefore you do this at your own risk.

    When we used to make low pressure loads to slug a barrel by firing a lead bullet through it into waste rags with a light charge of XXX powder we would get these backed out primers very often.

    Solutions are to size the cartridges with the least possible setting back of the shoulders that you can. Or to re-check your reloading manual and bear in mind that starting loads are just that. Loads to START at and that going below the suggested starting load is not to be advised by more than 5%.
    Last edited by enfieldspares; 14-03-2014 at 01:15.

  4. #4
    Quote Originally Posted by Whitebeard View Post
    Sooty cases are caused by poor case obturation which in many scenarios is caused by Lee collet dies not sizing the case necks down sufficiently to give enough neck tension on the bullet.

    Ian.
    Hi Ian
    I am using a Redding neck bushing die with a size 292 bush which I believe to be producing the correct neck tension. The cases are Norma and have be reloaded maybe 4 times.

  5. #5
    Quote Originally Posted by enfieldspares View Post
    Backed out, rather than totally blown out of the pocket, primers can be a sign of low pressure. How it works is that initially in all cartridges the primer starts to back out. Then as pressure increases the bullet and the case start to move. The bullet down the barrel and the case as far as the front face of the bolt. Effectively re-seating the primer.

    Solutions are to size the cartridges with the least possible setting back of the shoulders that you can. Or to re-check your reloading manual and bear in mind that starting loads are just that. Loads to START at and that going below the suggested starting load is not to be advised by more than 5%.
    Hi Enfieldspares
    I have been told by others that it could be low pressure related but I can't understand why like I said I've had it occur now with three different loads all with different projectiles and powder and none I believe are below the starting load recommendations. Also it doesn't happen with every shot, the other day it did it first shot then never again after.

    Here are the loads I've used -

    42 grains of Hogdens 4895 with Sierra 85 grain HP projectile.
    44.9 grains of Viht N160 with Sierra pro-hunter 120 SP.
    46 grains of Reloader R19 with Hornady interlock 129 SP.
    Last edited by Munty_Hunter; 14-03-2014 at 07:03.

  6. #6
    I'd guess the cause to be poor obturation with a strong liklihood the cases now need annealing.

    After correct annealing the hardness of the brass preventing correct sealing of the case neck/shoulder in the breech, the brass will be softened to then enable correct obturation.

    Close attention to headspace dimensions when setting up F/L sizing dies is an important factor often overlooked. If too much brass is worked when F/L sizing, it doesn't take long for the brass to deteriorate to the point when cases will fail to seal in the chamber - sooty cases and a drop off in performance are good indicators. ATB
    Blaser K95 Luxus Kipplaufbüchse .25-06Rem. Zeiss 8x56, 110gn Nosler Accubond = Game Over!

  7. #7
    Quote Originally Posted by Munty_Hunter View Post
    Hi Enfieldspares
    I have been told by others that it could be low pressure related but I can't understand why like I said I've had it occur now with three different loads all with different projectiles and powder and none I believe are below the starting load recommendations. Also it doesn't happen with every shot, the other day it did it first shot then never again after.

    Here are the loads I've used -

    42 grains of Hogdens 4895 with Sierra 85 grain HP projectile.
    44.9 grains of Viht N160 with Sierra pro-hunter 120 SP.
    46 grains of Reloader R19 with Hornady interlock 129 SP.

    Try annealing the necks. They work harden with use and prevent proper sealing. Lighter bullets move easier, requiring less pressure to start, thus why you are getting soot on the lighter ones. Try annealing a few cases and try them. Solved it for me when I had the same issues with a 308

    Pete
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  8. #8
    I've just reloaded some full length resized cases now and will use them and see what happens. Is it possible that it's something wrong with the rifle that's causing it?

  9. #9
    Quote Originally Posted by Whitebeard View Post
    Sooty cases are caused by poor case obturation which in many scenarios is caused by Lee collet dies not sizing the case necks down sufficiently to give enough neck tension on the bullet.

    Ian.
    Not really a fair comment is it.
    What you mean is the die was not properly set up, regardless of make or type.

    Neil.

  10. #10
    Are your scales correctly calibrated? As mentioned above, try annealing some cases. Also get some new brass and some factory ammunition and see if you get the same issues.

    Regards JCS

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