I thought it was a fluke, but ProChrono's numbers don't lie

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  • oldpink

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    Well, I wanted to know what the maximum published loads for 10mm would do at the range with six different powders suitable for the cartridge, so I loaded five rounds with the same charge for each of the six powders, then went to the range with my ProChrono Digital to clock what I had loaded.
    All charges were weighed because these were maximum loads, all cases were Starline, primed with CCI #300 large pistol primers, with 155 grain Speer TMJ bullets seated at 1.260", and the temperature that day (yesterday) was in the mid-to-high 80s.
    I was startled by the performance I was getting, and here are the numbers.
    The powder and charge are listed first, followed by each of the five muzzle velocities, the average muzzle velocity, the Extreme Spread, the Standard Deviation, and the average muzzle energy:

    13.0 gr. AA#7 - 1596 + 1598 +1602 + 1602 + 1596 - 1598 Avg. - 6 ES - 3 SD - 879 FPE Avg.

    7.2 gr. Titegroup - 1596 + 1608 + 1606 + 1600 + 1600 - 1602 Avg. - 12 ES - 4 SD - 884 FPE Avg.

    9.2 gr. CFE Pistol - 663 + 1628 + 1626 +1624 + 1629 - 1627 Avg. - 911 FPE Avg.

    11.3 gr. HS-6 - 1638 + 1654 + 1650 + 1652 + 1656 - 1650 Avg. - 18 ES - 7 SD - 937 FPE Avg.

    6.4 gr. 700-X - 1660 + 1658 + 1658 + 1660 + 1662 - 1659 Avg. - 4 ES - 1 SD - 948 FPE Avg.

    16.0 gr. AA#9 - 1687 + 1685 + 1685 + 1683 + 1687 - 1685 Avg. - 4 ES - 1 SD - 977 FPE Avg.

    Below is a string of 20 shots fired with the 16 grains of AA#9 loads that I wanted to see for how the heated up barrel would affect velocities, which it clearly does, as you can see below:
    16.0 gr. AA#9 - 1707 + 1707 + 1713 + 1716 + 1716 + 1713 + 1711 + 1711 + 1711 + 1709 + 1724 + 1722 + 1722 + 1722 + 1724 + 1724 + 1727 + 1729 + 1724 + 1724 - 1729 High - 1707 Low - 1717 Avg. 22 ES - 7 SD - 1014 FPE Avg.

    The only anomaly is the first velocity figure for CFE pistol (663), which was obviously an error because the gun recoiled identically to the other loads that followed with that charge level, but that's also why I left out the extreme spread and standard deviation numbers for that one powder.
    I went into this expecting to get in the 1400 FPS level, but, as you can see from looking at the numbers, these muzzle velocities are incredible, with not one below the high 1500 FPS level!
    It's also clear that the barrel heating up for the final string of 20 loads charged with AA#9 increased velocities by a fair bit.
    Just for the hell of it, here is a photo of the ProChrono Digital's display for the high velocity number for that string:
    0924161557_zpsu4gve4zz.jpg

    0924161557a_zpsa3asdmtb.jpg



    I was particularly interested in what the brass looked like, especially in what the primer looked like, inspecting each case for flattened, cratered, or blown primers, there was no evidence of that either, as you can see from this photo of the recovered brass looking down at the primers:
    0924161700_zps8ttppmwu.jpg


    What do you folks think of all this?
    Are these safe, or do I need to reduce significantly?
    I mean, I was stunned to see that I was getting an average muzzle energy with that final shot string of 20 loaded with AA#9 of over 1000 foot pounds.
     
    Last edited:

    oldpink

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    What gun and bbl lenght?

    I get numbers like that out of my carbine, but the best I typically do out of a 6.6" bbl is 900fpe and I only load that in virgin brass.

    S&W 1006 (5" barrel length):
    Smith__Wesson_1006.jpg


    This was in virgin brass.
    Considering that Underwood is considered balls to the wall with 155 grain loads in this caliber normally getting 1400 FPS out of a 5" barrel, I'm wondering if I might be well advised to reduce my charge a few grains until I get no more than that, but as I said, the primers aren't flattened, cratered, or blown, so the pressure levels don't seem excessive, although only a transducer or copper crusher (obviously not the type of equipment that someone outside of the manual publishers or ammo manufactures will have) would give the full story regarding pressure levels.
     

    biggen

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    I have found that most book "max" loads for 10mm are a little conservative. I run all my 10mm loads at book max and have yet to have any pressure signs at that level. Now I have pushed beyond max and found pressure. I'm shooting a Glock 20 with a factory barrel and a Lone Wolf 6" and the factory will start producing smilies a bit quicker than the LW barrel.

    If I recall correctly the 1006 has a pretty well supported chamber, but did you find any smiles on your cases?
     

    oldpink

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    I have found that most book "max" loads for 10mm are a little conservative. I run all my 10mm loads at book max and have yet to have any pressure signs at that level. Now I have pushed beyond max and found pressure. I'm shooting a Glock 20 with a factory barrel and a Lone Wolf 6" and the factory will start producing smilies a bit quicker than the LW barrel.

    If I recall correctly the 1006 has a pretty well supported chamber, but did you find any smiles on your cases?

    Thanks for you comments.
    No, I just don't get smiles at all out of this particular gun, which seems to buttress what I've heard that the 1000 series S&W pistols have fully supported chambers.
    I definitely know what to look for with the primer from experience over twenty years ago, when I had some .30-06 loads that showed all three signs of pressure, with the first primer flattened all the way out to the edge of the primer pocket, the second having cratering and flattening, and the third being blown, but none of those signs is evident with these insanely powerful loads.
    One other thing that was interesting about those velocities was just how little extreme spread there was, at least with the first six strings before I experimented with that seventh string of twenty shots with the hot barrel.
     

    rvb

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    how confident in the chrono are you? can you borrow another? I know I'm pretty confident in mine, but it's backed up by years of also running my ammo through match chronos and seeing similar results. also, friends and I have checked our respective chronos by putting them in a line and shot for shot comparing results....

    just a thought since you are seeing a couple hundred fps faster than expected w/o pressure signs...

    -rvb
     

    oldpink

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    how confident in the chrono are you? can you borrow another? I know I'm pretty confident in mine, but it's backed up by years of also running my ammo through match chronos and seeing similar results. also, friends and I have checked our respective chronos by putting them in a line and shot for shot comparing results....

    just a thought since you are seeing a couple hundred fps faster than expected w/o pressure signs...

    -rvb

    I'm very confident in its numbers, since as my now broken ancient Shooting Chrony F-1 that I replaced with the ProChrono gave the same basic numbers with my favorite .30-06 load that the ProChrono does with that same load now.
    I will be backing these loads off a grain or two, though; if not for safety concerns, but out of concern for what excessive velocity will do to the hollowpoints should I ever need to use them for self-defense.
     

    shibumiseeker

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    I'm very confident in its numbers, since as my now broken ancient Shooting Chrony F-1 that I replaced with the ProChrono gave the same basic numbers with my favorite .30-06 load that the ProChrono does with that same load now.
    I will be backing these loads off a grain or two, though; if not for safety concerns, but out of concern for what excessive velocity will do to the hollowpoints should I ever need to use them for self-defense.

    My nuclear rounds are hard cast and intended for use in griz country. I don't know of any commercial HPs that can handle that velocity and be as effective.
     

    oldpink

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    My nuclear rounds are hard cast and intended for use in griz country. I don't know of any commercial HPs that can handle that velocity and be as effective.

    I have to agree.
    Not even the fantastic Gold Dot can withstand these velocities.
    The only bullet I can think of that might be able to do it is the Barnes XPB, but it would be a stretch even then.
     

    RMC

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    Have you had issues with Gold Dot or other bullets? I pushed some 357 Sig over 1500 fps and they shot great. I've had some rifle bullets fly apart but not before I exceeded 4000 fps. I know it's not apples to apples but I'm curious about the point jacket integrity comes into play with pistol bullets.
     

    shibumiseeker

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    Have you had issues with Gold Dot or other bullets? I pushed some 357 Sig over 1500 fps and they shot great. I've had some rifle bullets fly apart but not before I exceeded 4000 fps. I know it's not apples to apples but I'm curious about the point jacket integrity comes into play with pistol bullets.

    For a quality pistol bullet it's a non-issue. The bigger problem is having them grenade when they hit something solid and not penetrate as deeply or reliably as the same bullet with less velocity. You get a larger initial wound but less likely to hit vital organs.
     

    RMC

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    For a quality pistol bullet it's a non-issue. The bigger problem is having them grenade when they hit something solid and not penetrate as deeply or reliably as the same bullet with less velocity. You get a larger initial wound but less likely to hit vital organs.

    That indeed makes sense. I can see where the goals differ greatly between self defense loads and hunting loads regarding adequate penetration and too much. Thanks :)
     
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