Pressure issues...?

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  • Moorvogi

    Firearm Advocate
    Dec 28, 2014
    855
    I’m not seeing anything myself but with this being a bit over charged I figured I would double check the internets. I put one unfired piece of brass for comparison.


    174fba4ba097b80b2bc0bd603a3a82d7.jpg



    Sent from my iPhone using Tapatalk
     

    gwchem

    Ultimate Member
    MDS Supporter
    Dec 18, 2014
    3,434
    SoMD
    The one at bottom right was so overcharged that it popped the firing pin indent back out!

    Joking aside, they look fine to me.
     

    Magnumite

    Ultimate Member
    Dec 17, 2007
    6,561
    Harford County, Maryland
    Two on upper right look warm, cratered primers and looks like heavier ejector impression marks. Lower right next to unfired case...slight cratering. If these were cold weather (recent) developed loads most certainly warm weather will bring pressure issues.

    I had to zoom in to see it. The other cases look fine. None of the primers are square cornered so that is a good sign. Did you shoot them over a chrono?
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,811
    I'm not seeing any primer "flow". The all seem to still have their rounded edges. Might check firing pin protrusion though.
     

    Moorvogi

    Firearm Advocate
    Dec 28, 2014
    855
    Two on upper right look warm, cratered primers and looks like heavier ejector impression marks. Lower right next to unfired case...slight cratering. If these were cold weather (recent) developed loads most certainly warm weather will bring pressure issues.

    I had to zoom in to see it. The other cases look fine. None of the primers are square cornered so that is a good sign. Did you shoot them over a chrono?

    I built the load back in fall 2019 (aug/sept), just didn't use it as i was shooting other firearms. I tested a couple and they seamed fine so i rolled with it. Trying them again now makes them seem fine but so much more "mustard" than normal round. Hence the desire to dbl check via interwebs.

    These were shot last Saturday 2/22/2020, temps ranged from 30 to 48 degrees.

    I did indeed shoot them over chrono. 69gr bullet at 3365fps. They are 0.5 to 1.5gr over charged (depending on manual you consult).
     

    Magnumite

    Ultimate Member
    Dec 17, 2007
    6,561
    Harford County, Maryland
    I'm not seeing any primer "flow". The all seem to still have their rounded edges. Might check firing pin protrusion though.
    The shoulders of the primers look fine, I had mentioned that as well.

    I was referring to the crater around the firing pin indentation. I realize firing pin/firing pin bore clearance could cause this. But the on case seems to show some brass wipe in the ejector contact area of the case head. If it were my gun, I would keep using the load, cautiously until it was exposed to all condition. The mild overloading seems trivial at this point, possible due to anything which could cause a greater volume in the case.

    Intuitive pressure evaluations are usually taken together, i.e. primer appearance, brass indicators, etc.. A good check would to be use virgin brass, load the case. Measure the case head just in front of the ejector groove with a micrometer of .0001" precision (venier micrometer). Fire the round then remeasure that case. Compare the case head expansion to a loading manual. One would need to do this with at least 5 or 6 rounds to begin to get a picture. 20 - 25 rounds would be a more reliable indicator.

    You may consider using same make factory ammo to get a good idea of typical case head expansion in your gun.

    If this were my arm, I would fire it cautiously always observant of the fired brass. I would also fire this this load on hot days after that ammo has taken on a hot soak for a few hours. Not bake it in the sun, that is bad juju for any load. Just a hot humid day soak in the shade. If the pressure indicators are similar than I presonally would say it is okay in that arm.
     

    atblis

    Ultimate Member
    May 23, 2010
    2,011
    I am not a fan of reading primers unless they look really bad, but that occurs well past the point you should have stopped. Yours don't look that bad.

    I do see case head flow into the ejector cutout which I do consider indication of excessive pressure. I back off a little until that goes away.

    That being said, if you're inside published data, and your velocities are in agreement with the published data, I wouldn't worry about it too much.
     

    Speed3

    Ultimate Member
    Aug 19, 2011
    7,816
    MD
    I am not a fan of reading primers unless they look really bad, but that's well past the point you should have stopped. Yours don't look that bad.

    I do see case head flow into the ejector cutout which I do consider indication of excessive pressure. I back off a little until that goes away.

    That being said, if your inside published data, and your velocities are in agreement with the published data, I wouldn't worry about it too much.

    I personally would shoot this one all day, especially since the load was developed in late summer Aug/Sept(hot/humid). If you would have said you developed the load in Jan/Feb...I would be a little more cautious.

    Published data or "data books" are often very low. In my target gun(6x47L) running 107gr smk, published data says max with 4350 is 38.5gr pushes it @ 2922 fps. I've run it upwards of 39.8gr and just started to get ejector swipes. The chamber cut has lots to do with it also... ie long throat.

    Just did load testing over the weekend on seating depths...I'm running 39.6gr of H4350, 107gr smk @ 3054fps a little over 1/4 MOA. However, my dads rifle, also a 6x47L likes 39.0gr.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,811
    The shoulders of the primers look fine, I had mentioned that as well.

    I was referring to the crater around the firing pin indentation. I realize firing pin/firing pin bore clearance could cause this. But the on case seems to show some brass wipe in the ejector contact area of the case head. If it were my gun, I would keep using the load, cautiously until it was exposed to all condition. The mild overloading seems trivial at this point, possible due to anything which could cause a greater volume in the case.

    Intuitive pressure evaluations are usually taken together, i.e. primer appearance, brass indicators, etc.. A good check would to be use virgin brass, load the case. Measure the case head just in front of the ejector groove with a micrometer of .0001" precision (venier micrometer). Fire the round then remeasure that case. Compare the case head expansion to a loading manual. One would need to do this with at least 5 or 6 rounds to begin to get a picture. 20 - 25 rounds would be a more reliable indicator.

    You may consider using same make factory ammo to get a good idea of typical case head expansion in your gun.

    If this were my arm, I would fire it cautiously always observant of the fired brass. I would also fire this this load on hot days after that ammo has taken on a hot soak for a few hours. Not bake it in the sun, that is bad juju for any load. Just a hot humid day soak in the shade. If the pressure indicators are similar than I presonally would say it is okay in that arm.

    Agree on all, but I'm also considering the fact that we are viewing at a very magnified image. The ejector marks could maybe have been previously made(reloads?) and also exaggerated by the enlarged pic.

    Also, I have gotten firing pin craters similar to these with my ARs especially if I use Winchester primers. They tend to be a little on the soft side. Some of us like to put a slight beveled edge to our ejectors to head off future 'mushrooming' of same.
     

    John from MD

    American Patriot
    MDS Supporter
    May 12, 2005
    22,728
    Socialist State of Maryland
    Two on upper right look warm, cratered primers and looks like heavier ejector impression marks. Lower right next to unfired case...slight cratering. If these were cold weather (recent) developed loads most certainly warm weather will bring pressure issues.

    I had to zoom in to see it. The other cases look fine. None of the primers are square cornered so that is a good sign. Did you shoot them over a chrono?

    +1 on the top two. Others look fine.
     

    Biggfoot44

    Ultimate Member
    Aug 2, 2009
    32,877
    Answer #1 - While the two top right are comparitively showing more , they all * Look * ok .

    Answer #2 - As Magnumite said , primer appearence is very poor at guestimating pressures at relevant pressure levels . The only halfway reliable low tech method for judging pressures is case head expansion .
     

    Doco Overboard

    Ultimate Member
    As Magnumite said , primer appearence is very poor at guestimating pressures at relevant pressure levels.

    The reason is, that an improperly shaped hemispherical firing pin tip even with the correct protrusion can still allow primer cup flow-back with an in spec pin port.
    Because it's a hemisphere or circular shape.
    Simply put, if the radiused portion of the pin is larger than the port is wide the proportion of the spherical indent is longer and the port is not completely sealed.
    .073-.075 is the normally accepted standard to about .055 protrusion. This is for rifles, pistols and revolvers and shotguns.
    One more thing 2 actually on the same subject, if the pin diameter is much larger the chance for a pierced primer is greater because of the primer cups inability to flex inwards or at the very least a fracture or cut out around the cups radius. You could also say HS is critical here with a pin and port that are in spec just because the firing pin strike is off center due to the cartridge laying at the bottom of the chamber. Primer cups are weaker at the radius than at the center because they are work hardened when punched into a cup shape. if anyone ever finds a primer cup that is thicker or harder than another Id like see it because Im interested in that sort of thing.
     

    mac1_131

    MSI Executive Member
    MDS Supporter
    Jan 31, 2009
    3,280
    I've seen worse LOL. Don't ask me how I know. Back it down a little you should be fine. If you leave one out in the hot sun it could change things.
     

    Park ranger

    Ultimate Member
    Dec 6, 2015
    2,315
    Was this with a Remington 700? Aka crater maker. They are notorious for needing to have the bolts bushed.
     

    Moorvogi

    Firearm Advocate
    Dec 28, 2014
    855
    Was this with a Remington 700? Aka crater maker. They are notorious for needing to have the bolts bushed.

    Nope. This was a ruger american predator 22-250. CCI primers. I'm tempted to try some trailboss loads to see if the primer has that.. but to be honest.. i'm probably 1k rounds thru the gun at this point. and might be due for a measuring or 3.
     

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