.40 S&W Split Case Mouths

Discussion in 'Ammunition and Reloading' started by Dag, Aug 4, 2007.

  1. Dag

    Dag Guest

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    I've started having a major problem with split case mouths on my reloads. The last 200 rounds had 15 split cases :!: . I've shot several thousand rounds through other .40 S&W guns, with virtually no problems with case splitting. This appears to be specific to my Steyr M40-A1 (ie: my XD doesn't do it). I've noticed that all of the case splits start where a ding was present in the mouth, from a previous loading. The two photos below show some of the dings, with no case split, and several of the split cases. Note that every one of the case splits start at one of those dings. In general, the fired cases from my Steyr seem to have alot of scratches and dings (more visible in the second photo). Most of the split cases had been fired 3-5 times, based on the number of LCI dimples. So, are these case dings typical of all M40-A1s (or just mine), is it fixable and does anyone else have problems with case mouth splits? Any other thoughts? Thanks.

    Dag

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  2. Dag

    Dag Guest

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    Case Mouth Splits

    Sorry, I should have included info on my load data. I've used a variety of powders, including W231, Herco and TiteGroup. All of my loads are toward the top end of the factory load data, but none over Hogdon's max, so I should be within SAAMI limits. Cartridge OAL is max I can get away with for reliable feeding. Minimum taper crimp, but with good bullet tension (I check each round by pushing the bullet nose hard against the workbench, and see no bullet setback). Full length sizing, to where the sizing die just touches the case holder. I think that covers it all. Thanks.

    Dag
     

  3. breechplug

    breechplug Guest

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    DAG, this could be off base but there seems to be a lot of dents & scratches on you brass, is this range brass that you have roladed? Were the dents and scratches there before the last fireing? Mine is an M-40, but my brass is never beat-up like that. As for the cracks, they look as if the cases have been over used. What brand are the cases? In three of my loading books there are pictures of stress cracks such as yours. I hope this helps in some way, Craig.
     
  4. Dag

    Dag Guest

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    banged up brass

    Hi Craig

    Thanks for the response. Interesting that the four split cases in the photo are all Winchester (I had to go look). Looking at the other 11, there's a mix of headstamps, including Winchester, CBC (Magtec), Fiocchi, Starline and R-P (Remington - Peters). Much of my brass came from shooting WWB and keeping the cases, so much of my brass is Winchester headstamp, but none of it was from scavenging old range brass. I have bought commercial reloads, but they always look like factory new. I've noticed from the beginning that my M40-A1 was hard on the brass, but I don't know why. I think the ding on the case mouth is key to the splits, since every single case split has that ding mark where the split starts. Anyone else out there seen that little triangle-shaped ding mark on their brass?

    Something just occured to me: I've installed the plunger spring fix to help with weak ejection. So I'm going to try removing the plunger spring and see if it makes a difference. Maybe the cases are hitting the ejection port on the way out. Hmmm ...

    Dag
     
  5. nixon

    nixon Member

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    Could be a simple case of overused brass. I often get one or two from time to time with my 45 coz it's hard to keep count of how much they have been used. By the looks of your picture, they're seem to be used many times over than it has to. If you have time, inspect your cases after every cleaning and sort out the beat up ones.
     
  6. Dag

    Dag Guest

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    Follow-up Range Report

    I removed the plunger spring, and almost all of the brass damage went away. :D I still get head bonkers, and a few minor case scratches from the steel rails on the underside if the slide, but most of the case dings, and particularly the triangle shaped ding at the case mouth that started all of the case splits, went completely away. I believe I've still got too much extractor tension, and the cases actually rotate completely back into the breech face and get dinged by the breech face and LCI. That's my theory. Next trip, I'm going to take some cutters, and try clipping one coil at a time to see if I can find a place that fixes the weak ejection, but doesn't damage the brass. <sigh> ... still searching for the perfect ejection.

    Dag
     
  7. Wulf

    Wulf Premium Member

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    Hiya Dag :)

    Sorry ta see ya havin' any problems with your reloads. My question to other "1911 spring extractor fixers" is this, "Are any of ya experiencing any of the brass problems that Dag is with his M40-A1?" :shock: Please post your experiences and let's get to the bottom of this ASAP. Thanx. :)

    Wulf
     
  8. Dag

    Dag Guest

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    Dinged-up Brass

    Hi Wulf

    Thanks for jumping in to help. It doesn't look like many folks are having the same problem. I'm pretty well convinced that I just need to tweak the spring tension a little more, to get the extractor to behave itself. I did start the plunger spring installation a little differently than everyone else: I forced as much extra tension as I could, then backed off a coil or two at a time. Others just cut the spring to be the same length as the original extractor spring, and it worked. :oops: Sounds like a one of a kind problem. <sigh> It still feels great in my hand, feeds and extracts absolutely everything I've fed it and I DO love those sights! :D Hey, I've always got SAI to fall back on if I can't get it right! Thanks again.

    Dag
     
  9. MrApathy

    MrApathy Active Member

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    another thing that can be done is to stretch and compress the spring which will reduce its strength some.
    keep the same length but its kinda a pita to experiment with if your clipping would just ignore that.

    would suggest checking the chamber ledge. when my M40 was new the ejected brass hit the slide by the extractor hard and would dent
    also had the case bending against the top of the chamber but that has gone away completely.

    havent had anything like what you had happening.

    see cracks like that on A-Merc brass which is junk and thats with the first firing forget reloading that junk.
     
  10. West01

    West01 New Member

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    Howdi Dag,

    +1 Mr.A. Absolutely.

    Another thing that is a possibility is an issue of timing. Where the extractor spring is holding a little to long. When the barrel tilt up and the case is still partially in the chamber, the front edge of the empty case may rub hard on the the top chamber LCI/Alignment nipple (that fork tinging at the top of the rear of the chamber block). If you put some machinist blue ink on it, you may see a stain on the front of the empty case...just a thought.

    Cheers!

    West01
    :D
     
  11. Dag

    Dag Guest

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    Split Case Mouths

    Hi MrApathy and West01

    By chamber ledge, do you mean the lip inside the chamber, on which the cartridge headspaces, or the rear edge of the chamber, right at the top of the feed ramp? I've looked inside the chamber with a bright light, and I don't see anything unusual (no obvious scratches or burrs). I think West01 may be on the right track with timing. Hopefully playing with extractor spring tension will help. I exchanged a couple of PMs with Wulf, and my handloads may be on the hot side, so I'm going to back off alittle there and see if that helps any. I'll try clipping a few more coils tomorrow at the range, and maybe pull out the plunger spring altogether and try stretching the extractor spring some, instead. I'll let you know what I find. I really appreciate you spending your time helping run this down! Have a great day!

    Dag
     
  12. MrApathy

    MrApathy Active Member

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    where the LCI peep hole is.

    barrel in hand looking down the bore it would be the top rear edge of the chamber under the hood.
    on my M40 I got burrs there on my M9 nothing.
     
  13. Dag

    Dag Guest

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    Burrs

    Hi MrApathy

    Using a bright light and a jewler's eye loupe, I can't see (or feel) anything that looks like a burr. I have carefully polished the feed ramp and chamber, but that all looks good. I noticed that there are some pretty sharp edges, from the machining of the breech-end of the barrel, and I'll go ahead and polish those just enough to break the sharp edge. Also, at the range yesterday, I was NOT able to find a spring combination that ejected cleanly (no head bonkers) and didn't damage the brass. So for now I'm staying with the stock extractor spring. I'll go back and try a couple of boxes of my SD load and see what it does. At least this way, I can reload the brass I fire. [stock spring = no dinged case mouths] :?

    Dag