Confused

Discussion in 'Ammo & Reloading' started by vitkop, Jan 7, 2013.

  1. vitkop

    vitkop Member

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    Just got home from a camping trip. I reloaded round the fire, it was awesome. I noticed a some of my ammo showed signed of excessive pressure and I'm not sure why. It spooked me enough that I stopped shooting my reloads after only a few shots. I don't understand why I'm seeing signs, I'm using the minimum amount of powder for the bullet I'm using, I even brought a scale with me to double check my charges.

    What I'm seeing is a small faded line around the base of the case and the primer looks a little squished not crisp like the factory ones look like when they get shot

    Confused
     
  2. SHOOTER13

    SHOOTER13 RETIRED MODERATOR Lifetime Supporting

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    Well, some pics showing these "signs" would go a long way in helping us to help you.

    Also, the type of powder, the load info, the number of times the casings were used would be

    beneficial too...
     

  3. vitkop

    vitkop Member

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    Of course, sorry bout that. The brass was fired once, by me. The primer is CCI LR 200. 20.5 grains IMR 4198 powder, with a Sierra 150 Grain RN bullet

    image-3905494831.jpg

    The line is hard to see with the camera, it's front and center in the photo. More of a smudge really.
     

    Attached Files:

  4. R.Ph. 380

    R.Ph. 380 Well-Known Member

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    Is your reloading data for IMR 4198 or H 4198. IMR is a rod powder and Hogdon is a very very short kind of greenish rod. I think the IMR is actually faster than the Hogdon, although they are very very close. Might be that the IMR is a little faster and might be just that much hotter.

    Bill
     
  5. Hyphenated

    Hyphenated Well-Known Member

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    IMHO you don't have over pressure loads. My 30-30 brass all have a little bit of a ring around them similar to what you are experiencing. From the pictures I don't see signs of pressure on your primer. They appear very rounded. If the pressure was high the primer would be flat and you would have cratering around the firing pin strike. I think you have a low pressure load that did not seal the primer. It looks like gas blow by around the primer. That would indicate the primer didn't seal and may have backed out a smidgen allowing gas to get past causing that black mark.

    According to my Hodgdon manual 20grs of either H4198 or IMR4198 is 6grs below the 'starting load'. Two things you can do....first you can load more rounds adding 1gr at a time until you reach 26grs. You won't need more than two of each just so you can do a primer check. Shoot those and watch the primers as you go. Option number two is to switch to a faster burning powder if you want to stay with the low velocity loads. Unique and 2400 will reach higher pressures faster in reduced loads. This will help you get good expansion on your brass and primers while still being able to shoot 1400-1600fps loads.

    I use 16grs of 2400 with a 150gr GC cast bullet. This data is available in the old 44th Edition Lyman manual. Best of luck.
     
    Last edited: Jan 8, 2013
  6. greyhawk50

    greyhawk50 Well-Known Member

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    ^^^ I completely agree with Hyph ^^^

    It is difficult to visualize what happens in the chamber at the instant of ignition because it all happens within milliseconds. But there is a sequence of events.
    The firing pin strikes the primer and it ignites. The powder begins to ignite near the primer and burns forward and outward.
    As this happens, the primer moves back to make contact with the bolt face. The case begins to expand and seal the chamber as the case is forced back towards the bolt face and re-seats the primer.
    The faster the powder burns, the more instantaneous this process occurs thus allowing for less gas leakage.
    Signs of over pressure can be seen by looking at the primer. As Hyph stated, the surface of the primer will be completely flat with a crater around the primer punch mark. The bolt face will also leave tell-tail rings on the primer (a mirror image of the machined surface on the bolt face). In cases of extreme pressure, the primer will fill the gap (ring) between the primer and the case head. This can be confirmed by punching the primer out and checking to see if the surface resembles the rim of a 22 lr. (where the face of the primer is larger than the diameter) because the primer is expanded prier to being re-seated in the case.
    This is a slow-mo explanation of what happens in an instant.

    As per the photos, the surface of the primer is still crowned and the outside edges are still rounded. Plus, there is still a ring/gap between the primer and the case head. I see no signs of over pressure.
    I hope this helps.

    Guys, If I missed anything, help me out.
     
    Last edited: Jan 8, 2013
  7. vitkop

    vitkop Member

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    I'm sure you guys are right and I probably misdiagnosed the problem. I got the load info from Lyman's 49th. Ill add a grain at a time till I like what I see. I still don't understand where that ring comes from, none of the factory round have it after its been shot
     
  8. Hyphenated

    Hyphenated Well-Known Member

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    I can't be 100% sure on this, but I will hazard a guess. The bottom 3/16" on your case is the thickest and strongest part. It does not expand much if any compared to the upper 90%. When you fire the rifle the upper portion expands and touches the chamber walls...the very bottom portion does not. At this junction you get a ring. The ring becomes even more pronounced when you run the case through a sizing die during reloading.

    I have a similar ring on my 30-30 brass and I don't load any of them above SAAMI pressure. As a matter of fact, most of my 30-30 ammo is reduced loads using cast bullets. Gas checked cast bullets at 1600fps are fun and inexpensive to shoot.

    I would like to add it was a good job on your part to inspect the brass. As a reloader it is always smart to watch your brass for signs of pressure. A fired case can tell you a lot.