Pressure flats

Discussion in 'ELR, Ballistics & Bullets Board' started by tomswede, Jan 8, 2018.

  1. tomswede

    tomswede

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    Guess I was a bit vague. Question really was intended for longer ranges, 600 yards and up. My personal interest is prone mid and long range, so in match conditions 20 shot strings.
     
  2. retired

    retired

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    but LARGE targets ? mil is a 2 moa 10 ring.
    if palma i do not know sizes.
    but not benchrest with a 20 shot string.

    see how a little LACK of info skews things.

    all have a good day

     
  3. tomswede

    tomswede

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    Still need good performing loads and good methods to develop them. Since the “flats” don’t make sense to me I wanted to gain some knowledge on what people do and the results they were getting.
     
  4. fredo

    fredo

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    Some shooters prefer a more 'quick and dirty' type of ladder testing to find that 'high node' that Meangreen explained so well in his post #44 above. Others seem to enjoy the actual load development & testing to the point that they prolong it to the point of exhaustion. Different strokes...

    Soon I'll be venturing into somewhat uncharted waters when finding some working loads for my .220Redline wildcat. Being a wicked overbore killin rifle, my testing will be most definitely 'quick & dirty'. With preliminary QUICKLOAD data in hand, I'll run a few 8-10 shot ladders at 2-300yds with chrono rolling. Will look for that 'flat spot' on target while watching for a 'flat spot' on the chrono that may betray an impending pressure spike. Shouldn't take but 50 rds to have something safe and accurate enough to take to the field and prove out at distance. Rifles and components are built so well these days that it don't take much to find a fine shooting load...
     
  5. CharlieNC

    CharlieNC Gold $$ Contributor

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    That's very close to what I do as well, with the charge range being narrowed down based on OBT using Quick Load. I do like to shoot 2 per load to have more confidence, specifically that a single "flyer" if in a scatter node can be misleading as appearing to be in a node based on comparison to its neighbors.
     
  6. milanuk

    milanuk Team Savage Silver $$ Contributor

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    ^^^ this!
     
  7. dmoran

    dmoran Gold $$ Contributor

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    RL16  7022016.png

    Used up all 4' of the target board (and a little extra) on that one..... lol
    Typical amount of Velocity to POI curves that I see, in ladder testing.
    Donovan
     
    Last edited: Jan 12, 2018
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  8. retired

    retired

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    what do you think of rl16 ?
    i have not had a chance to try out what i bought.
    comming from an rl15 shooter.

     
  9. dmoran

    dmoran Gold $$ Contributor

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    Switched to it from RL15 (using those same components) in both my LT & HV Guns.
    Was repeatedly getting a little less vertical with the RL16, and its more temperature stable.
    It does require a longer funnel, to drop the charges, for the 6Dasher cases.
    Higher load density so powder crush also comes into play when seating bullets.
    Was already on long throats (.160" FB), which helps for the extra fill.
    Also find it to be "pressure friendly".
    Donovan
     
    Last edited: Jan 12, 2018
  10. Alex Wheeler

    Alex Wheeler Gold $$ Contributor

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    Dang that dashers almost getting BRA-BRO velocities :D
     
  11. dmoran

    dmoran Gold $$ Contributor

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    @Alex Wheeler
    That barrel is +3" longer then BRA-BRO, would be part of the reason.
     
    Last edited: Jan 13, 2018
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  12. Alex Wheeler

    Alex Wheeler Gold $$ Contributor

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    Not bad for 33ish grains of powder?
     
  13. milanuk

    milanuk Team Savage Silver $$ Contributor

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    Interesting... if going just by vertical displacement, I'd almost pick something else. But going by MV...
     
  14. rhovee

    rhovee

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    I'm really curious what you end up with. Or if you ran that charge out to 1k how it would do. Thinking about trying this test out in my hunting rifle.
     
  15. Bart B.

    Bart B.

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    I've found Sierra Bulllets' load data helpful in calculating the fps velocity change per 1/10th grain change in powder charge. Their velocity increments are 100 fps. Divide a 100 fps velocity change charge weight change by the number of tenth grain powder increments.

    If a 1.5 grain in charge weight changes a velocity 100 fps, 100 divided by 15 equals 6.7 fps change per tenth grain change in charge.

    For example, here is Sierra's 308 Win load data; search for this phrase then use the CityMaker 6mmbr link to download the file

    "sierra 308 win.pdf"

    Calculate a bullet-powder data change for each 100 fps band then note the fps per tenth grain change for each band.
     
    Last edited: Jan 21, 2018
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  16. retired

    retired

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    i think you need to call sierra about your math and their numbers.
    i doubt any 2 loads came out in 100fps steps.

     
  17. Bart B.

    Bart B.

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    Here's Sierra's 100 fps velocity steps for 308 Win with 175 and 180 grain bullets:
    Screenshot_20180121-140835_crop_315x488.jpg

    Not good enough for you? It's high school math and curve plotting. It shows trends and approximation. Same as all load data based on anyone's objectives, standards and conditions.

    If not, then you tell Sierra about it. It's their data. I'm just the messenger. I shoot back.
     
    Last edited: Jan 21, 2018
  18. retired

    retired

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    It shows trends and approximation.


     
  19. dkhunt14

    dkhunt14

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    That is just a rough guideline. Different barrels, even from the same company can really change the velocity. I've had fast barrels and slow barrels. Also different lengths can really change it also. Usually a longer barrel is faster. I have also had slow lots of powder and fast ones and the velocities really change . Matt
     
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  20. Bart B.

    Bart B.

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    Of course, it's a guideline. That data I put up showed what one set of components produced.

    There will be different velocity numbers across different ways the rifle is held. Several people will have different velocities with the same rifle and ammo; I've seen over 50 fps spread in average. Each lot of powder and primers will have their unique set of velocity numbers over a small range.
     
    Last edited: Jan 24, 2018
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