Quickload's OBT feature

Discussion in 'Reloading Forum (All Calibers)' started by fatelvis, Jan 22, 2019.

  1. fatelvis

    fatelvis Silver $$ Contributor

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    Just playing with Quickload and waiting for warmer weather, and was wondering if any of you use the OBT feature. If so, does it work, or at least act as a shortcut to finding a great load? Thanks Guys.
     
  2. Zero333

    Zero333 Silver $$ Contributor

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  3. fatelvis

    fatelvis Silver $$ Contributor

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    Thanks Zeo. Is that table from the Quickload program?
     
  4. Ned Ludd

    Ned Ludd Silver $$ Contributor

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    AFAIK - QuickLoad does not have an "OBT feature", unless perhaps it's a new feature only on the very latest version. OBT, or optimal barrel time, is a concept develop by Chris Long, as noted above by Zero333. His published tables of optimal barrel times are really all you need. Just match the barrel time output (in milliseconds) from QL to a specific OBT listed in the table for your barrel length. It can certainly be a good predictive tool, but you still need to shoot a range of charge weights surrounding the predicted OBT node. In my hands, optimal precision is usually found at a barrel time just a tick slower than predicted in Chris Long's table. For example, Node 4 for a 30" barrel in the Table is 1.3684 ms. In my hands, tuned loads for this node generally run in the 1.371 to 1.376 ms range, or slightly slower than predicted. Nonetheless, QL can expedite the process and help you get close.
     
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  5. fatelvis

    fatelvis Silver $$ Contributor

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    Very cool. I can't wait to chrono my load and tweak the powder speed to match. And then the fun begins! Thanks guys.
     
  6. fatelvis

    fatelvis Silver $$ Contributor

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    Is barrel length measured from muzzle to bolt face?
     
  7. Wildcat455

    Wildcat455

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    Yes it is.
     
  8. Jeff A

    Jeff A Formerly known as BikeEffects Gold $$ Contributor

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    There is a learning curve but QuickLOAD has saved me a lot of money and time.
     
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  9. uncle-buck

    uncle-buck

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    How?
     
  10. savagedasher

    savagedasher

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    Probably because he can choose the powder that fill the case amount he wants He can see the case capacity and check then adjust the max pressure
    He can put all powders made and look at the pressure and amount of fill
    The biggest thing he can see pmax
    And the p1
    Then he can see how much of the barrel it takes to Get 95% off the speed
    And the % if the powder is burning in the barrel and kill sketters
     
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  11. Jeff A

    Jeff A Formerly known as BikeEffects Gold $$ Contributor

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    That pretty much says it all. The powder you don't waste because they aren't appropriate and if you burn powder you use primers and bullets. Now that I'm shooting Long Range Benchrest, I'm thinking more and more about barrel cost. Thyey do wear out!
     
  12. Bart B.

    Bart B.

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    Keep in mind the fact 10 barrels from different makers the same length chambered with the same reamer can have a 50 fps or more spread in average muzzle velocity with the same load. Your barrel probably ain't exactly the same as the ones Quickload's data is derived from.
     
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  13. savagedasher

    savagedasher

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    Primers and different lots of the powder can add another unknown
     
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  14. fatelvis

    fatelvis Silver $$ Contributor

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    Just when I start getting the 'warm and fuzzy" feeling that I'm onto a shortcut to the ultimate load, you guys wreck my buzz! Lol
     
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  15. Bart B.

    Bart B.

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    I originally thought like you in that post
    I like to think we were sharpening your knowledge and reasoning knives so you can cut the reloading mustard a little bit better.
     
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  16. rammac

    rammac

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    QuickLoad doesn't show an OBT node, it produces a value called Barrel Time that represents how long the bullet is in the barrel and Barrel Time is equivalent to an OBT Node.

    It's pretty obvious that the average shooter does not have the technology to produce lab grade data but if you use a little common sense you can produce valid reference information in regards to muzzle velocities, chamber max pressure, bullet base pressure along the the barrel's length, etc. Most people that think that QuickLoad doesn't work don't understand that all data is relative based on some standard and with QuickLoad you have to adjust that standard until you get a match with real world data from a chronograph or a pressure transducer. You can adjust the baseline assumptions (using the recommendations of the software's manual) to match the data from your measuring devices. Once you get a match between the predicted data and the true data then the software will allow you to make "what if" predictions that will be very close the real world. My predictions are usually within 25 FPS of my actual measured values, most often the software is low. Taking in to consideration that the accuracy of the typical commercial chronograph can is about plus or minus 7 FPS of the true bullet speed, then the actual bullet speed is some value within a 14 FPS range and comparing that to my results that are within a 25 FPS range I'd say that the software can produce pretty accurate results (all numbers based on a muzzle velocity of 2500 FPS).

    Once you educate yourself on how to use the software you can save money and time developing loads because you can eliminate loads that you know wont work - pressure chamber too high, muzzle velocity way off from what you want, powder produces the wrong pressure/time curve, etc.
     
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  17. savagedasher

    savagedasher

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    Most shooter don’t check case capacity when loading
    To me it’s the most important thing in reloading fo accuracy
     
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  18. Bart B.

    Bart B.

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    How is case capacity best measured for most precise volume numbers:

    • New cases.
    • Fired cases.
    • Resized fired cases
    • Resized fired cases full into the sizing die.
    I prefer the last one because all the cases have the same outside dimensions and their inside volume is not influenced by out of round case issues.
     
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  19. savagedasher

    savagedasher

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    I like twice fired and you don’t size them the chamber has done it for you
    I’m struggling to load bullets for my grandson to shoot this weekend
    Should isn’t working right yet
    I haven’t loaded anything After I broke my shoulder
     
  20. fatelvis

    fatelvis Silver $$ Contributor

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    I believe Quickload suggests using a fired case, before resizing, for cartridges over 30k pressure,
     
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