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Case failure

jonkjonk Member Posts: 10,121
edited January 2002 in Ask the Experts
Took my 6.5 Dutch Mannlicher out shooting for the second time the other day and experienced massive case failure on three shells. One had the head seperate completely, the others broke when I examined them at home. I was using reforemed .303 brass. I don't know the load info as I bought it from another gunbroker user. Previously I had fired surplus military ammo with no signs of trouble at all. See attached pic; the intact case is the military case, the blown one is the .303. So what gives? To hot a load? Bad brass? Result of reforming? I might add that the .303 resized stuff chambered a bit tight as the rim is slightly larger and thicker, but it did not require undue effort either, or I wouldn't have done it.
"...hit your enemy in the belly, and kick him when he is down, and boil his prisoners in oil- if you take any- and torture his women and children. Then people will keep clear of you..." -Admiral of the Fleet Lord Fisher, speaking at the Hague Peace Conference in 1899.
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Comments

  • luger01luger01 Member Posts: 230 ✭✭✭
    edited November -1
    Jonk,Bend a paperclip with a hook on one end and strightened long enough to reach the bottom of a case from inside and use it to "feel" if there is a shallow spot near the head (about where they seperated). If there is (pull a loaded round and try this after you empty out the powder, too), then the cases have been stretched past safe margins and you need to pull and save the bullets and toss the rest.All I can say is, "Buying handloads from a stranger has caused many problems for many shooters".By the way - I'm really glad you weren't hurt!!! ;^)[This message has been edited by luger01 (edited 01-22-2002).]
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  • 218Beekeep218Beekeep Member Posts: 3,033
    edited November -1
    Jonk,I had that happen with old reloaded ammo,which had barely noticable deterioration in the exact same location as the seperation on the case in your picture.I swear that I did not try to sound like Jessie Jackson,or Johnny Cochran..it just came out that way..218
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  • gunpaqgunpaq Member Posts: 4,607 ✭✭
    edited November -1
    Jonk: I had the exact same thing happen to me several years ago using new factory "Mag Tech" .357 ammo in both my Marlin and Rossi. Your picture is identical. Five rounds out of a box of fifty failed, only shot thirty rounds out of the box. Returned to gun shop with the deffective rounds and was given a new box of Remington ammo. They did not believe what happened over the phone. Have not used Mag Tech since.
    Pack slow, fall stable, pull high, hit dead center.
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  • v35v35 Member Posts: 12,710 ✭✭✭
    edited November -1
    Check your headspace.
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  • v35v35 Member Posts: 12,710 ✭✭✭
    edited November -1
    To be more correct; compare the height of the shoulder of an unfired case with that of a fired but not separated case. If it isnt a headspace issue, it's likely either bad foreign brass, or it has been resized too much from an oversized chamber where the brass just forward of the web is alternately stretched and reformed, fatiguing it or from brass flow forward fom firing and thinning to the breaking point just above the base.
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  • talontalon Member Posts: 150 ✭✭✭
    edited November -1
    Once fired .303British cases are always suspect. The military rifle chambers are way oversized so any shells fired in them are really stressed. When sent thru the resizing die they are stressed again. It won't take much of this mistreatment to cause case seperation. Then, too, what I see in your pictures is a classic footprint of excessive headspace. Luger1 and V35 have good words here. (It wouldn't hurt to check headspace in your rifle, too)
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  • jonkjonk Member Posts: 10,121
    edited November -1
    So if it is a classic footprint of excessive headspace, why did the surplus ammo (factory ammo if you will, designed for this chamber) show no signs of headspace problems? This is a rimmed cartridge, so I believe I am correct in saying that headspace is a function of the rim. As .303 is thicker and larger in diameter, and the bolt is fairly tight on closing (needs about 2X the force of the mil surplus) it seems that the rim is ok....OOH WAIT! I bet I GOT IT! Maybe the rim isn't even entering the chamber because it is TOO thick and TOO big in diameter, so the case is blowing out! Any thoughts?
    "...hit your enemy in the belly, and kick him when he is down, and boil his prisoners in oil- if you take any- and torture his women and children. Then people will keep clear of you..." -Admiral of the Fleet Lord Fisher, speaking at the Hague Peace Conference in 1899.
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  • Der GebirgsjagerDer Gebirgsjager Member Posts: 1,673 ✭✭
    edited November -1
    Did I understand correctly that the .303 brass has been previouly loaded and fired by a former owner? If so, Talon is probably on the right track. That is exactly where the case head will fail on the second or third loading if fired in a No.1 Mk.III with excessive headspace. Incipient case head separation is usually visible after the first firing if the brass is tumbled before reloading. Trouble caused by the rim diameter and/or thickness is a possibility easily checked on with a micrometer; but I'd bet on the first scenario.
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  • Guns & GlassGuns & Glass Member Posts: 864 ✭✭✭✭
    edited November -1
    Tip gotten from an ole timer. Make dummy rounds (no primer & powder).Color/paint the case in question, and a known good case with something like black magic marker. Must clean well for it to color completely, and deeply. Chamber, and cycle couple times being careful not to let full extraction occur.Compare OAL, and markings against each round.If rims, cases, etc., are out of spec, you will be able to see different marks at different spots,and compare. Clean chamber when done.
    Happy Bullet Holes!
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  • v35v35 Member Posts: 12,710 ✭✭✭
    edited November -1
    Please look at my clarification of headspace with a rimmed bottleneck cartridge. If the dimension from the boltface to the shoulder on the chamber is .006" or more than the corresponding dimension from the base of the cartridge to its' shoulder then you have excess headspace where the case is shorter than the chamber.If the brass in the shoulder area is relatively soft, on firing the shoulder will expand and fill the chamber with minimal stretching and you will see sharp corners on the shoulder. However, if the brass is hard and springy in the shoulder area the case will stretch and tend to separate just forward of the web.Since you are using cases shortened & reformed from 303 British you have moved the shoulder back behind the neck annealed area where the brass is now thicker and tougher.You need to anneal the brass before you reform the case by standing them in an inch of water, heating the caseneck with a Bernzomatic torch and toppling them over when the discoloration goes about 1/8" below where the new shoulder will be.
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