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Thread: case/neck hardness - can it cause failure to seal (lack of obturation)?

  1. #1

    case/neck hardness - can it cause failure to seal (lack of obturation)?

    I have some Lapua .243 cases which to my knowledge have only been fired between 2-3 times.

    recently I have found that I have some cases that I am firing for the first time are showing soot much further back towards the head than I would expect.

    The only thing I can think of is that they were fired considerably more than the "once fired" when I got them!

    It doesnt seem to make any difference if it is a low, medium or hot load.
    I have some test loads from the other day which I knew would probably be too hot and sure enough they are just beginning to show pressure signs but the neck is sooty almost down to the shoulder.

    Would annealing make a difference or should I junk them and start fresh?

  2. #2
    If you have soot back past the shoulder and onto the case body that means the whole case is not sealing properly, which is usually a sign of to low a powder charge.
    Are you using a Lee collet die?


  3. #3
    thats a good inicator of work hard brass ,get them annealed properly

  4. #4
    Ive use these top job,well worth it saved me buying new brass

  5. #5
    Unless you are using very light loads, and you are getting soot past the shoulder, toss the brass. Annealing back that far under DIY conditions can be risky.

    Collet dies won't cause that condition. Even if a neck is barely holding onto a bullet, the pressure should seal the chamber unless the loads are light. I have deliberately colleted "light" on my .222 and let the leade seat the bullet into the case for target shooting. These rounds always obturated enough to seal the case.~Muir

  6. #6
    its not consistent, that is my problem.
    The loads have been a variety of 75 through 100gr .243
    I ran three shots of 43.6gr N160 under Berger 90gn BTBT, which is far from light!, case heads showed some light pressure signs, soot mark went down neck and about 1/3 of the shoulder.

    Others are 1/3 down the neck and look normal.
    some have gone past the shoulder.

    weird thing is the groups are fine. 1/2" 100yd group with 100gr Interlocks, 3/4" 130yd group with 75gn Vmax!

    All brass has been neck sized only (by me at least!), chambers fine, ejects fine.
    Cases look normal, no signs of mass firings, headstamp is clear and lettering deep.

    I suppose annealing would be worth a shot to at least give them one last chance before scrapping them!

  7. #7
    if you anneal with tempilaq paint 650-750 deg f you cant mess up the case ,its better to do it on the machine i have the benchsoarse best investment i made to my long range set up as you get great consistency from case to case down to the micro second
    i have compition brass fired nearly 20 times on full power loads and i get .250 moa vertical or better at 1000yds ,brass degrades and work hardens after about 3-4 reloads even in a custom chamber with good dies ,so a factory chamber has a lot more room to move and size down
    for a stalking rifle you wont notice it at 100 mtrs but at long range you will ,but its worth annealing in my veiw saves a bit of money for you ,or if you have deep pockets just bin the brass and buy new

  8. #8
    Quote Originally Posted by taylor View Post
    if you anneal with tempilaq paint 650-750 deg f you cant mess up the case ,
    I have thought about doing it myself but the tempilaq comes in 50deg increments. do I go with 650, 700 or 750?
    or I could just send them to you !

    The other option is I bite the bullet, so to speak and bin them! I do have access to some (true) once fired norma from a friend but probably would get them for a few months!
    dont really want to drop 100 on new brass

  9. #9
    750 deg f is what i have used for years done it manualy with great success ,but if you want me to do it on the machine its 10 a 100cases plus delivery but they will be annealed properly,or if your passing dundee drop them off

  10. #10
    Quote Originally Posted by see it shoot it View Post
    Ive use these top job,well worth it saved me buying new brass
    Cripes have you seen his prices? You can buy once fired for that.

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