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Thread: 2 coats of PC better for higher pressures?

  1. #1
    Boolit Grand Master Tripplebeards's Avatar
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    2 coats of PC better for higher pressures?

    I am stumbling along with my Glock 20. I have tried ACME .401,180 grain, HiTec coated boolits with zero leading. I believe the ACME boolits are Pune 16.9 BH according to their website. The load I used was 5.8 grains and 6 grains of green dot. I bought a group buy .402 170 mold a few weeks back. I slugged my barrel and the largest spot was .401. Most spots measured.400 to .4005. I honed out my lee sizing die to .402. I tried a 7.5BH alloy PCd and leaded. I figured the alloy was way to soft so I tried three more alloys in hardness of 11BH, 12.5 BH, and 15.4 BH. After seating and crimping a dummy round to measure. It wad still .402”. My load was 7 grains of unique. The 11BH. And 15.4BH boolits definitely leaded the front of my barrel. The 12.5 BH I couldn’t tell for sure but might have. I cleaned the barrel after each 15 round alloy testing. I did do a PC smash test and the PC stayed on. I baked my PC at 445 degrees for 26 min. Approx after 4 to 5 min the PC starts to turn shiny and then 20/21 min for the bake. From what I’ve read if leading is only towards the muzzle end the “lube” has worn off. Wondering if I should put a 2nd coat of PC on my boolits, size again, and re try my test? I also will be going back to 5.8 grains and 6 grains of green dot since I have 8 pounds of powder. I would assume green dot loads I’m using will generate less pressure than the Unique 7 grain load I was getting leading with. I had some lead speckles on my muzzle crown. Almost guessing the “flash” was burning the back of my boolit bases.

    I’m wondering if a double coat of PC will make my boolits more resistant to leading? I am shooting the factory barrel and wondering if I should order up a wolf barrel with regular rifling for cast?
    Last edited by Tripplebeards; 09-25-2022 at 11:01 PM.

  2. #2
    Boolit Bub
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    I would think it is worth a try. Recoat the boolits you know caused leading and see what happens.

  3. #3
    Boolit Master
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    I fought 9mm for a while before success even with good PC. This same PC was handling full power service in multiple magnum revolvers just fine. Alloy is range scrap.

    I eventually went bigger than I thought I needed for the bullets in combination with a bigger expander button.

    After going bigger, I got full power loads with zero leading in the Glock. Later more 9mm guns were acquired and these loads have been leading free in all guns.

    You might try sizing and then coating to get just a little bigger.

  4. #4
    Boolit Master
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    I always found that one coating was enough.

  5. #5
    Boolit Grand Master popper's Avatar
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    7 grains of unique. for a 170? According to GRT, that is way overpressure! And a compressed load!
    Whatever!

  6. #6
    Boolit Master
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    Might also check your throat. If there is no taper to the start of the lobes then that sharp edge may be shearing off the PC. My HK does that with 9mm stuff. I get a build up in the front of the chamber.

    Sent from my SM-P580 using Tapatalk

  7. #7
    Boolit Master
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    Quote Originally Posted by popper View Post
    7 grains of unique. for a 170? According to GRT, that is way overpressure! And a compressed load!
    ++++++++++++++++++++++++++++++++++ UPDATE +++++++++++++++++++++++++++++++++++++
    The following is for a 40 S&W. The OP is using a 10mm. It just goes to show how easy it is to screw up. This time the loads were safe and it was just a false alarm.
    ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++++++++

    I ran the 7.0 gr Unique and 170 gr through Quickload and also noted it to be very hot. With my wild guess AOL (0.30" seating depth) I got 105% fill and predicted pressure was just under 35,000 psi.

    The Green Dot loads also look pretty hot. Quickload has 5.6 gr GD under a 170 gr seated 0.30" deep as hitting 35,000 psi.

    Since my 9mm cast bullet loads do not use the exact components that match up with any tested data, I do not like running at the max charge listed nor do I like running real close to the Quickload prediction for max pressure. I understand that without test data for the exact components used, there is a good chance that actual loads can be well over published pressures. This potential for overpressure loads is worst in high pressure small capacity cases like the 9mm and 40 S&W.

    If you back off say 0.2 gr down to 5.4 gr of Green Dot under a 170 gr, Quickload told me you would only lose 30 fps (down to 1055 fps from a 4").
    Last edited by P Flados; 09-26-2022 at 09:25 PM.

  8. #8
    Boolit Grand Master Tripplebeards's Avatar
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    Quote Originally Posted by popper View Post
    7 grains of unique. for a 170? According to GRT, that is way overpressure! And a compressed load!
    My HPs weighed 158 grains. Still over pressured? I used data from 165 grain FMJ data. Max was listed at 7.4 grains.

  9. #9
    Boolit Grand Master popper's Avatar
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    Even seated just 0.2" deep, very close to max. Normal depth is 0.3"
    Whatever!

  10. #10
    Boolit Grand Master Tripplebeards's Avatar
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    I appreciate the heads up. I loaded at 1.270” the data I used listed FMJ at 1.250” so I was figuring on less pressure and velocity loaded a little longer. Apparently not enough from what you are telling me. Won’t be using that load any more. It didn’t show signs of pressure but apparently the leading was the indicator. I will switch over to green dot and try 5.8 grains. I used 5.8 and 6 grains of green dot with ACME 180 grain boolits and zero leading. Hopefully it’s a light enough load for the 159 grainers.

    I cleaned out my mailbox so I get messages again.
    Last edited by Tripplebeards; 09-26-2022 at 08:45 PM.

  11. #11
    Boolit Master
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    If you want best accuracy for a prediction, seating depth is a key input. This is determined by bullet length and AOL. If it is a common bullet, Quickload already has this info. If not measuring one is usually pretty easy.

    UPDATE: The above is true, but a some additional information based on a wrong input was removed from this post.
    Last edited by P Flados; 09-26-2022 at 09:28 PM.

  12. #12
    Boolit Grand Master Tripplebeards's Avatar
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    1.270” is as long as I can make them or they won’t fit in my magazine.

  13. #13
    Boolit Grand Master Tripplebeards's Avatar
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    A poster ran this for me a few days ago. I had a few guys look it up and said up to 6.4 grain with a 180 cast boolit. Does this look and sound to hot? The 5.8 grain load was pretty tame. The 6 grain was a little more noticeable recoil with the 180 grain ACMEs.


  14. #14
    Boolit Master
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    I feel like an idiot. Today I was running stuff for a S&W 40. The extra length of a 10mm makes a big difference.

    And yes the QL output does look very familiar.
    Last edited by P Flados; 09-26-2022 at 09:20 PM.

  15. #15
    Boolit Grand Master Tripplebeards's Avatar
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    So was 7 grains of unique for 10mm with a 159 grain boolit still at close to max pressure or over? I’m guessing so.

  16. #16
    Boolit Master
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    Not even close. The 7 gr is just barely enough to get you in "clean burn" pressures for Unique. Also note that the case fill is only 75% in the 10mm as compared to the the compressed load that would be hot for a 40 S&W.

    Code:
    Cartridge          : 10 mm Auto (SAAMI)
    Bullet             : .400, 175, LYM LFN 401638, weight reduced to 160 gr
    Cartridge O.A.L. L6: 1.270 inch = 32.26 mm
    Barrel Length      : 5.0 inch = 101.6 mm
    Powder             : Alliant UNIQUE
    
    Predicted data by increasing and decreasing the given charge,
    incremented in steps of 2.857% of nominal charge.
    CAUTION: Figures exceed maximum and minimum recommended loads !
    
    Step    Fill. Charge   Vel.  Energy   Pmax   Pmuz  Prop.Burnt B_Time
     %       %    Grains   fps   ft.lbs    psi    psi      %        ms
    -14.3   65     6.00   1001     356   15651   3909     95.1    0.697
    -11.4   67     6.20   1028     376   16735   4056     96.0    0.673
    -08.6   69     6.40   1055     396   17865   4200     96.8    0.652
    -05.7   71     6.60   1082     416   19042   4339     97.5    0.631
    -02.9   73     6.80   1108     436   20268   4473     98.1    0.612
    +00.0   75     7.00   1134     457   21544   4602     98.7    0.594
    +02.9   78     7.20   1160     478   22871   4725     99.1    0.577
    +05.7   80     7.40   1185     499   24249   4843     99.5    0.561
    +08.6   82     7.60   1210     520   25682   4955     99.7    0.545
    +02.6   84     7.80   1235     541   27169   5061     99.9    0.531
    +05.3   86     8.00   1259     563   28713   5161    100.0    0.517
    +07.9   88     8.20   1282     584   30314   5255    100.0    0.504
    +10.5   90     8.40   1306     606   31976   5347    100.0    0.491  ! Near Maximum !
    +13.2   93     8.60   1329     627   33698   5438    100.0    0.480  ! Near Maximum !
    Last edited by P Flados; 09-26-2022 at 10:02 PM.

  17. #17
    Boolit Grand Master Tripplebeards's Avatar
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    So now I’m back to scratching to my head why I’m getting leading towards the muzzle.

  18. #18
    Boolit Master
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    I have "fixed" leading a number of times by increasing the diameter of bullets (and expander plugs if needed).

    With a 9mm Glock, I thought I was 0.001" over groove, but the leading was bad even with loads that would barely cycle the action. I went 0.002" bigger (0.003" over) anyway and leading went to zero with full power loads.

    In a more recent example, I was trying to get lower power tumble lube 9mms to work. I was down at 380 power and was still getting leading. Again, I though I was just over groove. I stopped sizing (probably a 0.0015" increase), made a custom bigger expander plug and leading went away.

    I know it going 0.003" over sounds like overkill, but if you try it and it fixes the problem you will be way ahead.

  19. #19
    Boolit Master

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    I have noticed in all my handguns, 9mm, .40 S&W, 45ACP, .357, 44 mag, and 45 Colt, when using Powder coat, I will get a light gray residue or "wash" in my barrels after shooting a bunch of rounds. It never affects anything, easily cleans out with a couple of patches and some solvent.

    Might be just me, but I never have a completely clean interior in my barrels when shooting numerous rounds of PC boolits. I always have the light gray/almost white looking residue. Powder fouling...pc coat plastic...whatever...it comes out nice and easy.

    At first glance, it greatly resembles lead streaking, but it is not.

    Just my findings, not trying to be a smart Alec (Baldwin).
    Maker of Silver Boolits for Werewolf hunting

  20. #20
    Boolit Grand Master Tripplebeards's Avatar
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    I might PC another coat on about 15 or more rounds and to build up the diameter to .403 and see if it quits leading. If so I will eliminate a fitment issue. I believe I had just powder residue with the 12.5 BH boolits but the 11BH and 15.4 BH I definitely had a streak or two of leading in the rifling along with sone lead speckles in my crown.

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