Brass troubles

Discussion in 'Reloading' started by JAWZ, Jul 27, 2008.

  1. JAWZ

    JAWZ Well-Known Member

    Messages:
    187
    Joined:
    May 2, 2008
    I was at the range today testing out the new 180gr E-tip bullet and a box of 180gr Hornady interlock when I ran into an interesting problem.

    I was using brand new brass and the rifle is my 300wby mag in MKV accumark.
    The first loads of E-tips there was no problems at all no preasure signs easy bolt lift the whole shebang. But when i fired the exact same powder charge with the interlocks i was getting powder burns down the side of the case all the way to the head and still no preasure signs.

    Then on the 4th shot in the group i extracted the case and found that it had caved in on 1 side of the shoulder. :( I just dont undrstand how this could happen.


    [​IMG]

    I understand that gas is escaping around the side of the case but how, is it because of the canalure?
    Any help or sugestion to what may have caused it would be awsome.

    Andrew
     
  2. boomtube

    boomtube Well-Known Member

    Messages:
    1,595
    Joined:
    Oct 8, 2007
    Such dents are caused by gas running back down the chamber when firing loads too low in pressure to expand the case enough to form a seal.
     

  3. larrywillis

    larrywillis Well-Known Member

    Messages:
    192
    Joined:
    Mar 18, 2002
    JAWZ ........

    That's one of the worst cases of "delayed detonation" I've ever seen, and it can be dangerous. This happens when your powder doesn't ignite properly. It's caused by a weak primer or a deteriorated powder. As the powder ignites it burns partially, then the blast re-ignites the rest of the powder - after it's half way down the barrel. That creates rearward pressure as it tries to escape around the outside of your case. Let the ammo manufacturer know, and they'll gladly send you a new box. (At least their lawyers will.)

    (This is one good reason to use magnum primers whenever using a large amount of powder in huge case.)

    - Innovative
     
  4. MagnumManiac

    MagnumManiac Well-Known Member

    Messages:
    1,002
    Joined:
    Feb 25, 2008
    boomtube is right on the money, that is caused by too little pressure, not delayed ignition or hang fire.
    The reason it has happened is because you changed components without working up the load again, the same would happen if you went from a Barnes to an Interlok also. The all copper bullets develop higher pressures with less powder than most conventional jacketed bullets, therefore you need to add more powder to get the same pressure value.
    Whenever you change components you need to start again with about a 5% reduction from the max load and work back up to the previous load, same for changing powder lots.

    THIS IS VERY DANGEROUS! you could have ended up with a destroyed rifle, it is known as S.E.E. (Secondary Explosion Effect).
    MagnumManiac.
    gun)
     
  5. larrywillis

    larrywillis Well-Known Member

    Messages:
    192
    Joined:
    Mar 18, 2002
    MagnumManiac ........

    I agree. It's definitely not a hangfire or a delayed ignition. However, "delayed detonation" happens when a full powder charge doesn't ignite properly. As the primer fires, SOME of the powder detonates and pressure builds inside the case. As the powder burns, if flows forward and some of it doesn't ignite (for about nanosecond). During this delay the chamber pressure is slightly reduced. When the rest of the powder reignites in the barrel, the pressure spikes upward again and blows back towards the case (that is no longer completely sealed). The whole chamber is then resealed from the secondary explosion, but not before blowing back between the case and the chamber wall.

    (This could also be a good sign to use magnum primers if not already using them. You could also switch to a powder that is easier to ignite.)

    - Innovative
     
  6. woods

    woods Well-Known Member

    Messages:
    965
    Joined:
    Jun 4, 2006
    That dent is also a classic sign of a case head separation

    [​IMG]
    [​IMG]

    in which the gas is also transversing from the neck area to the case body area. In the above pics and case head separations it would be that the gas is going out the separation and going forward to escape out the bore. Without a blown primer or a separation my guess would be that it is going from the bore/neck area towards the case body and case head.

    Interesting.
     
  7. larrywillis

    larrywillis Well-Known Member

    Messages:
    192
    Joined:
    Mar 18, 2002
    woods .....

    Actually, even though both symptoms occurred for you at the same time . . . . they are totally unrelated. Headspace separation is caused by your cases being stretched too far (after pushing the case shoulder too far back when resizing). Firing the case blows it back to fill your chamber, and that can easily rip your case in half.

    - Innovative
     
  8. woods

    woods Well-Known Member

    Messages:
    965
    Joined:
    Jun 4, 2006
    Actually, no. I always monitor the gap between the case shoulder and chamber shoulder and resize for a partial crush fit by pushing the shoulder back .0005" to .001". In this particular case it was probably due to the excessive space between the new case shoulder and the chamber shoulder (not really headspace in a belted case) of .026" and the thinness of the Norma brass. That would have caused more thinning than usual on the initial firing, but no way to alleviate that other than forming a false shoulder or purchasing a hydraulic form die.

    This was discussed in length on another forum Case head Separation - Topic Powered by eve community and the consensus was that is was gas coming out of the case head separation and going forward. The pressure would have escaped in the early stage from the separation and created a path to the front.

    But this is all supposition unless someone knows of a scientifically conducted experiment.
     
  9. larrywillis

    larrywillis Well-Known Member

    Messages:
    192
    Joined:
    Mar 18, 2002
    woods ........

    After looking at your link, it appears that other shooters are also experiencing case dents caused by gas escaping during case separation. Those are usually unrelated symptoms, but it's easy to understand how case dents can also form during case separation.

    It just takes a little attention to detail to make handloads exactly correct, and avoid all those accidents. Shooters need to be aware that when handloading belted cases, you need to always headspace on the shoulder - not on the belt.

    - Innovative
     
  10. woods

    woods Well-Known Member

    Messages:
    965
    Joined:
    Jun 4, 2006
    Yes, that's correct. Always headspace on the shoulder but you have to get there first. Unfortunately, most if not all the brass manufacturers put twice as much space between their new brass shoulders and most chambers.

    There is one other method which might alleviate case stretch at the web and that is seating the initial seating of the bullet well into the lands to keep the firing pin from pushing the case forward. That is what I do now but I don't have any definitive proof it actually accomplishes anything.

    Anyway, guess we're hijacking this thread.

    BTW, since you are an entrepeneur of repute in reloading gear, why don't you pick up the slack that Hornady is leaving with a hydraulic form die. It wouldn't necessarily have to be custom made for a specific chamber, just have it push the shoulder out and the reloader could push it back where he wanted. If you use that I should get free dies for life from you, agreed?
     
    Last edited: Nov 23, 2008
  11. davewilson

    davewilson Well-Known Member

    Messages:
    2,634
    Joined:
    Feb 19, 2004
    the original post doesn't, at least to my observation, have any case head separation or cracking problem. Weatherby's have extremely long throats. a problem that can occur with a long throat is the bullet bearing surface will release from the neck before it engages into the rifling. this alows the pressure to get behind the case instead of staying inside of it. i'm betting the bearing surface length of the all copper E-tip is longer than the interbond. long enough to engage in the rifling before it releases from the case keeping the pressure where it's supposed to be. the Hornady is probably a little shorter and is allowing the pressure to get behind the case causing the dents.
     
  12. boomtube

    boomtube Well-Known Member

    Messages:
    1,595
    Joined:
    Oct 8, 2007
    "Actually, even though both symptoms occurred for you at the same time . . . . they are totally unrelated. "

    Yep.
     
  13. larrywillis

    larrywillis Well-Known Member

    Messages:
    192
    Joined:
    Mar 18, 2002
    Getting back to the original post . . . .

    There was no case separation. It was just mentioned by a shooter that considered associating case separation to this symptom. A short bullet in the long throated Weatherby rifle is a very good theory.

    However, I have this pisture on my website that shows a 300 Wby, a 300 Win Mag, and a 300 Win Mag case that was fired in a 300 Wby rifle by mistake. There were no case dents there. The shooter didn't examine his fired cases until he fired 3 or 4 rounds, and none of those cases had dents either. Surely this situation had a rather long jump to the rifling. (By the way, don't try to duplicate this shooters mistake!)

    [​IMG]


    Do I still believe that the cause is irratic powder detonation? . . . . yep.

    - Innovative
     
  14. davewilson

    davewilson Well-Known Member

    Messages:
    2,634
    Joined:
    Feb 19, 2004
    it's not a theory, it's a fact that happens with long throats. not every combination will produce dents.

    maybe the original poster would see if his bullets are in the rifling before they exit the case. would be very informative if we knew in this situation.

    this was just discussed a couple of weeks ago on here.