Too Much or Not Enough Powder?

Discussion in 'Ammunition & Reloading' started by Trez, Aug 25, 2011.

  1. Trez

    Trez Well-Known Member

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    How do I tell if my loads are too much or not enough? I was reading that not enough powder can cause over pressures...

    Im developing a load for my Arisaka, Previous loads I made show that 40 grs of RL-15 were starting to bulge cases, So I made some with 36 grs. My first batch worked great, but the second batch I made with 36 grs. started to bulge cases.. (I used a 150 gr. bullet on both)
    Doing some online reading Ive read that the 7.7 should be able to take between 35 and 45 grs. of RL-15... Guns & Ammo Magazine had load data for the 7.7 Arisaka between 40 and 45 grs. using a 174 gr. bullet.

    Im not even close to the maximums so why are my cases bulging? The last batch that didnt work, the cases were already fire formed and I just neck sized them.... Am I loading too light?
    The 7.7 case doesnt allow for a double charge, and I check all my cases anyways for double charges, so I dont think that was the culprit.

    Ive read that you can use heaver data on lighter bullets, but not the other way around. Can I use the data for the 174 gr. on the 150 gr.?

    Thanks for any help!!
     
  2. Lindenwood

    Lindenwood New Member

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    The only way light loads can cause overpressures is if there is a very small amount of powder such that when the cartridge is horizontal, the powder lies below the flash hole. Thus, this requires notably less than half a case full.

    Could it be an out-of-spec chamber? What kind of bulging do you mean?

    And yes, you can use data for a 174gr bullet under a 150gr bullet.
     

  3. JonM

    JonM Moderator

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    Seating bullets too deep can cause it too.
     
  4. Trez

    Trez Well-Known Member

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    Ok, then the loads not too light.. the case is about 3/4 full..

    Would it make a difference if I went from a boat tail to a flat based bullet? all my manuals show the same loads for both.

    How do I know if I seated the bullet too much, I thought I was good as long as I stayed above the shoulder. The bullet is under OAL, so I could seat it slightly less. Can you seat a bullet to little?

    I didnt crimp the bullet, should I?

    I wouldnt think the chamber is outta spec. ive shot the Arisaka 3-4 times and the last time was the first time its really done it.
    Ive Even shot some full power loads of 4895 in reformed 30-06 I got off a friend they were loaded to 2,800 fps. and they worked perfectly.. (they were reloaded in 1960 according to the date on the box)
     
    Last edited: Aug 25, 2011
  5. noylj

    noylj Member

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    The only way I have heard that it might be "possible" for a light charge to cause a over pressure spike is to use a powder that is slow for the cartridge and be a very light load. The hypothesis, which I have never read having been proven, is that the whole charge ignites simultaneously and causes an "instantaneous" pressure spike (the nominal or average pressure will still be low).
    There is not way that this can happen within the normal range of loads likely to be shot. This applies to folks trying to shoot "gallery" loads and NOT being smart enough to move to a faster powder.
    It may be a myth, since I have never seen any proof from controlled experiments, but it is still a myth that has certain limits that many people seem to ignore.
    In the world of internal ballistics, your rifle and your cases will tell you. Has your rifle been checked by a 'smith to verify that there is not excess head space and the chamber is in good shape?
     
  6. hiwall

    hiwall Well-Known Member

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    If you only neck size that negates the effects of excess headspace, so not likely that is the problem. Pics of the bulged case next to a normal one would be very helpful. Excess oil in the chamber or case lube on the cases can cause problems. You double checked your bullets to see if they are the correct diameter? These bullets were the same ones that worked in the first batch? Check the case length(case only not with bullet) - if to long that can cause problems. Hard for the case to bulge if supported by the chamber correctly. If no pics then describe the bad cases(where is the bulge).
     
  7. Trez

    Trez Well-Known Member

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    How do I know what the proper seating depth is? I read its the diameter of the bullet but thats longer than the neck is..
     
    Last edited: Aug 25, 2011
  8. JonM

    JonM Moderator

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    load manual. but the best method is an overal length gauge from hornady. if they dont offer a case for your rifle just used an empty fired case drill and tap the bottom of the case to fit the gauge
     
  9. BillM

    BillM Active Member Supporter

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    Are you trimming the brass to length? It's possible that too long brass
    can get into the leade and get "trapped" between the bullet and barrel.
    This can impede bullet release and cause a pressure spike even with light loads.
     
  10. Trez

    Trez Well-Known Member

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    I finally figured it out!! I was way over seating the bullet... :eek:
    Man, you guys are good! THANK YOU!!
    Im glad it was a Arisaka... Its strong enough let me learn from my mistake..... :eek:
     
    Last edited: Aug 25, 2011
  11. moneymaker17

    moneymaker17 New Member

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    but thats only if its below miniumum oal right?
     
  12. jpattersonnh

    jpattersonnh Active Member

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    The easiest way to determine OAL in a specific rifle is:
    Take an empty case, not resized, but trimmed to correct length.
    Slightly sqeeze the neck so it will hold the bullet.
    Put the bullet in the case, just barely.
    Very carefully chamber the dummy round.
    Carefully extract the round and mark the bullet at the case. Measure the OAL of the dummy cartridge and seat a real bullet .05 deeper when loading cases. Keep the dummy cartridge for the future and write all of your info in a book.
     
  13. JonM

    JonM Moderator

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    Minimum oal is the point at which your gun blows up....

    Seriously though...

    Seating bullets below the depth at which the load data was created starts increasing the pressure in a sharp nonlinear curve. Its ok to go longer so long as the bullet isnt touching the lands when chambered.
     
  14. moneymaker17

    moneymaker17 New Member

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    so if im in the middle of minimum OAL ,, and Max OAL
    i will be good.
    i dont seat the bullets anywhere near the min oal
    for instance

    min OAL= 2.165
    Max OAL = 2.260


    and the lowest case lenth i made is around =2.212
    then i should be fine.

    because please correct me if i am wrong but.
    i have a case trimmer
    (the kind for the drill then you have the bar(made for you specfic lenth) then you have a case trimmer ball...
    if i put it in that "jig" it still isnt long enough to trim it, so im i believe i dont have to trim correct?????
     
  15. jpattersonnh

    jpattersonnh Active Member

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    You only trim if the case is too long. Try my method, you will have more accurate ammo.
     
  16. lief69

    lief69 New Member

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    I hope you are using Norma cases. 7.7 bases are about.480 so 30/06 cases at .473 wil bulge excessively if used to make 7.7 brass. Norma cases are larger and correct at the base. I tried to make 7.7s from "standard" brass 45 years ago and found then suitable for one shot with reduced cast bullet loads.
     
  17. Trez

    Trez Well-Known Member

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    I have some Norma 7.7 cases and they only measure out to .473? My reformed .30-06 measures out to .470... Shooting the Norma factory ammo was worse than my reloads.... My Arisaka seems to like the thicker military reformed .30-06 than the factory Norma 7.7 brass...