357 Mag Bullet Jump Problem

357 Mag Bullet Jump Problem

This is a discussion on 357 Mag Bullet Jump Problem within the Reloading forums, part of the Defensive Ammunition & Ballistics category; I have been playing around loading some 357 mag 158g LSWC HP. Load the J frame up, shoot 4 shots then measure 5th round. It ...

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  1. #1
    VIP Member Array Stevew's Avatar
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    357 Mag Bullet Jump Problem

    I have been playing around loading some 357 mag 158g LSWC HP. Load the J frame up, shoot 4 shots then measure 5th round. It is longer every time. I have increased the amount of crimp to the point that the case is into the lead. The bullet jump is not so bad that I am concerned about cylinder lock up. These are not hot loads, 4.8g of 700X and speer LSWC HP bullets. Just slightly hotter than 38spl +P. Recoil is not bad from my S&W Mod 60, but you know it isn't a 38spl. How does BB pull it off.
    Good people do not need laws to tell them to act responsibly, while bad people will find a way around laws. Plato


  2. #2
    Senior Member Array Devilsclaw's Avatar
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    Well the case probably should be into the lead. Without seeing a loaded round, it's hard for me to make a call. Make it look like a factory round. Might try some heavier crimp. What kind of brass is it? How hard are the bullets, do you know?

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    VIP Member Array farronwolf's Avatar
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    Am I understanding correctly that you measure the rounds for OAL before putting them in the gun. Shoot some of the rounds and then measure the 5th round for OAL after shooting 4 and the OAL has changed?

    Are you saying that the 2nd, 3rd and 4th rounds don't change OAL, just the 5th one? Is it in the same place in the cylinder each time, or does that matter at all?

    I can honestly say, I have never had a problem with OAL changing, at least not that I have ever noticed.

    The only other thing I could suggest is to change to a lead that has a cannelure so that the crimp has something more to hold on to.

    This has me sort of puzzled actually.
    Just remember that shot placement is much more important with what you carry than how big a bang you get with each trigger pull.
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  4. #4
    VIP Member Array glockman10mm's Avatar
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    Have you chronographed your load to see exactly what it's doing? It may be a little hotter than you think. If it is what it should be according to your load data, then it's probably a proper crimp issue.

  5. #5
    VIP Member Array Stevew's Avatar
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    I am not checking until the 5th round, I would assume that each round jumps and it progressively gets worst with each shot. I am crimping to the verge of crumpling the case. The bullets do have a cannelure. It does not matter what hole in the cylinder the last round comes out of. The brass is once fired Winchester.
    Good people do not need laws to tell them to act responsibly, while bad people will find a way around laws. Plato

  6. #6
    Distinguished Member Array razor02097's Avatar
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    The case should not be crimped into the bullet it should be properly crimped so the bullet isn't damaged.

    That is a lot of powder for a lead bullet.... How come you want to push it so fast? Try taking it down to about 3 - 3.5 grains of 700X. If you want to push it faster you might want to consider a different powder.
    There is something about firing 4,200 thirty millimeter rounds/min that makes me feel all warm and fuzzy inside.

  7. #7
    VIP Member Array Stevew's Avatar
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    Quote Originally Posted by glockman10mm View Post
    Have you chronographed your load to see exactly what it's doing? It may be a little hotter than you think. If it is what it should be according to your load data, then it's probably a proper crimp issue.
    I haven't chrono'd yet. I spent most of the afternoon adjusting the crimp and testing in hopes of getting the bullet jump to stop. By the way, I am not using magnum primers. I will break out the chrono and give them a check. I will also run a few rounds through my GP100 and see if the heavier gun stops the bullet jump, not that it will be any help. I was hoping to just be able to load up a handfull of 357 Mag LSWC HP that ran about 900 fps from a snub nose.
    Good people do not need laws to tell them to act responsibly, while bad people will find a way around laws. Plato

  8. #8
    Distinguished Member Array razor02097's Avatar
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    That may be asking a lot from a lead bullet. You might try an actual magnum load but it would likely give you the same bullet unseating issue.... maybe not...

    According to my Hornaday recipe book

    Bullet 158 grain LSWC
    Primer WSPM
    Powder choices to make a velocity = 950fps through an 8" barrel 1/16" twist

    Clays = 4.4 grain
    Unique = 5 grain
    VIHT N-340 = 5.5 grain
    AA No. 5 = 7.3 grain

    Be careful as these are the "max" loads the book recommends.
    There is something about firing 4,200 thirty millimeter rounds/min that makes me feel all warm and fuzzy inside.

  9. #9
    VIP Member Array farronwolf's Avatar
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    Hodgdon website says the maximum powder charge for a 158 gr lead bullet is 4.9 grains of 700x at 1137 fps, so your pushing what the manufacturer says the limits are.

    Speer 13 shows 158 gr SWC with a maximum charge weight of 5.0 grs of 700x using small pistol primers.

    Like some others have suggested, you might try to back off the powder charge or chrono the rounds to see what velocity your getting out of them.
    Just remember that shot placement is much more important with what you carry than how big a bang you get with each trigger pull.
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  10. #10
    VIP Member Array Stevew's Avatar
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    I chrono'd the ammo today.
    GP100 4in barrel
    AVG 917 fps

    S&W Mod 60 2 1/4 in barrel
    AVG 829 fps
    standard deviation 14

    I did not have any bullet jump today with 20 rounds (5 cyclinders). Yesterday every cylinder full had bullet jump when I checked COAL on the last round. The COAL was jumping from 1.600 to 1.612. I do not think it will be to difficult to get the extra 71fps that I was going for, I think I will just call it good enough. Accuracy is very good at short range. Leading isn't too bad. Now I need to do some groups at 50 yards to see if it is a round that will be a good all around low powered 357 mag round. I am looking something that can pull double duty as a SD round and be a good load for cottontails.
    Good people do not need laws to tell them to act responsibly, while bad people will find a way around laws. Plato

  11. #11
    Distinguished Member Array coffeecup's Avatar
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    I do believe you are pushing the limit a bit. Back off the 700x or switch powders !

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