HBN - Hexagonal Boron Nitride - cold bore shot

Discussion in 'Reloading' started by Pons, Nov 17, 2012.

  1. Pons

    Pons Well-Known Member

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    Hello to all,

    I've been watching the cold bore shot on some of my rifles. On one of them, it is very consistent. First cold shot is .75 to .5 moa low, then the point of impact rises, group holds well, then after fouling increases, point of impact rises again.

    This isn't really a problem, because it is predictable. However, I heard one of the claims of HBN is that it has the possible advantage of having the cold bore shot shooting with the rest of the group.

    I am curious and I'm going to give it a shot. I'm going to track the velocity of the rounds, find out when I get the velocity drop (indicating reduced pressure, therefore indicating reduced friction), develop a good load for the coated barrel, and after that happens I'm going to see about cold bore shots vs groups. Since I want to start with a cold bore and I'm waiting on materials yet, this project is going to take a while.

    I thought I would post this in case any one else here has already done this and or is curious about how it might turn out.
     
  2. green 788

    green 788 Well-Known Member

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    If the load is properly developed, the cold bore shot will stay with the rest of the group... Using my OCW system of development, you can get your rifles to shoot like this--without any special chemicals or gizmos...

    [​IMG]ccb + 2 follow ups

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    It really can be done. :)
     

  3. jhibbard24

    jhibbard24 Well-Known Member

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    So what's the secret
     
  4. royinidaho

    royinidaho Writers Guild

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    To me the "secret" is finding the powder charge, or very small range of powder charges, that result in the smallest achievable groups from a given rifle.

    The powder charge may vary as much as +/- one half a grain and for all practical purposes (hunting) groups will be small and symmetrical for some pretty good distances.

    I've notices that ES/SD may be all over the place with this "optimum" powder weight but groups out to 400 yards and maybe a little better are very consistent.

    Using 5 or 6 different charge weights in 0.5 gr increments and shooting round robin will reveal the optimum charge weight (OCW).
     
  5. green 788

    green 788 Well-Known Member

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    thanks Roy... and yes, that's it.

    Then follow up with seating depth adjustments to fine tune the load. Adjusting seating depth AFTER you've identified the OCW is the icing on the cake (and reason number one why I don't use or recommend bullets that are seating depth sensitive)...

    Lastly... don't inflict death-by-unga-bunga on your barrel when it comes time to clean... a couple passes with a good solvent... maybe soak the bore in Hoppes number 9 afterward... and it's more than clean enough. Look up Todd Hodnett's video on this on youtube... that's how I've been doing it for years, and it works.

    Dan
     
  6. Mikecr

    Mikecr Well-Known Member

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    Pons, Personally, I use WS2 for prefouling but HBN might work well.

    If you take your barrels to CLEAN, which is more than a couple patches of Hoppes, there is typically a need for shooting to foul the bore. If you leave oil in the bore, it takes 5-8 shots to burn out & reach stable fouling. Also, some guns simply will not cold bore shoot with warm bore groups.
    I had a Tubb2000 that would cold bore shoot, or hot bore shoot no problem, but from cold to hot bore there was a full 1/4moa of POI shift(often bigger than my grouping).

    I solved the pre-fouling issue with all my guns by cleaning bores completely, drying them, and then dry burnishing with tungsten(WS2). My bullets are also coated.
    With this, my first shot fits within a typical five shot group from cold, -for guns capable.
    I can put my guns in the safe dry and know when I pull one, and drop it in the dirt on a bipod, the first shot IS good.

    Load is only one part of cold bore shooting.
     
  7. jhibbard24

    jhibbard24 Well-Known Member

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    roy- i have also noticed extremes with ES and SD numbers on my most accurate load. i achieved the load by using ladder testing and therefore got the only load the i've been able to get to shoot sub 1/2 MOA consistently (.38 moa)
     
  8. jhibbard24

    jhibbard24 Well-Known Member

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    and cold bore shots so far have been dead center everytime. BTW this is on a very lightweight sporter hunting rifle with a finnicky, pencil thin barrel