• Winner! Quick Shot Challenge: What’s the dumbest shooting myth you’ve heard?

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Recent content by jbmillard

  1. J

    JBM Ballistics question, FNG question.

    The drag function models I use (given to me by Bob McCoy) are a function of mach number. (See the G1 here http://www.jbmballistics.com/ballistics/downloads/text/mcg1.txt.) Note that it increases as the mach number decreases for supersonic flight. The drag is proportional to the velocity...
  2. J

    JBM Ballistics question, FNG question.

    No need to ask me "WTF". You can read what I wrote in post 22. Brad
  3. J

    JBM Ballistics question, FNG question.

    I think you should put in whatever is correct.
  4. J

    JBM Ballistics question, FNG question.

    Difference was explained above. Just make sure that your density altitude really is 5000 feet when the temperature goes to 105 degrees. Just because that's your altitude doesn't mean the density altitude is that. As for what Ballistic AE is doing, no clue. Brad
  5. J

    JBM Ballistics question, FNG question.

    Which data? Velocity and temperature? In the fields provided in the trajectory card calculator.
  6. J

    JBM Ballistics question, FNG question.

    There are high and low temperatures and associated velocities. I wouldn't know how to begin with powder type. When I do it, I put five or ten rounds in a ziploc bag and stick it in ice water before I drive to the range. I then shoot those five or ten in rapid succession over the...
  7. J

    JBM Ballistics question, FNG question.

    When you specify density altitude, you are completely defining the density, independent of temperature you entered. Temperature is used to calculate corrected muzzle velocity usung the correction factor and zero temperature you enter. Temperature is also used to calculate the speed of...
  8. J

    Gunsmithing Thread profile question

    I agree what the previous posters have said. Use the Machinist's Handbook. To see it, look here: Unified Thread Standard - Wikipedia, the free encyclopedia It's what I've always done and it works well. Brad
  9. J

    Considering taller press for 338LM

    Since you said you were open to other suggestions, I would recommend an arbor press and hand dies for seating. I do this for my .338-416. I use my Rockchucker to resize and then hand dies for seating. This also allows me to do load development at the range. Brad
  10. J

    Entering DA in JBM Ballistics

    That's correct if you want to use the trajectory program. If you want to create a trajectory card, just enter the altitudes at the bottom of the form -- they are density altitudes.
  11. J

    wilson seating die?

    I used them for rifle cartridges. I won't speak the accuracy potential because I've not tested the difference. For me, it's more a matter of convenience. I prime a bunch of cases and then take my powder measure, B-Square arbor press and Wilson dies to the range and do load development. I...
  12. J

    Range Report Checking Zero at match Location

    When you zero your rifle, you are setting the angle between the line of sight (centerline of the scope) and the bore. When you go to a different altitude, this doesn't change -- but the drag on the bullet does. This change is very small and most people that use a trajectory calculator probably...
  13. J

    222 loads

    4198 I used to have a Sako Riihimaki in .222 Remington. Nice rifle, just couldn't get parts for it anymore. I used about 20.5 to 21.5 grains of IMR 4198. It was very accurate with just about any bullet from 50 to 52 grains.
  14. J

    Gunsmithing Rustoleum instead of Krylon

    Another option Not to hijack a thread here, but another option is the model airplane paints made for RC aircraft. I tried some a number of years ago and they worked very well. I did let it harden for a couple of weeks. I used the stuff that was supposed to be able to take RC plane fuel...
  15. J

    you know what would be cool

    I tend to agree with you. Most of the ones that I've see seem to try to give you a ballistics table that doesn't take everything into account. That's why I made my own ("BallistiComp"). Even though, I decided not to market it (at least for now), it's nice to have a computer that automatically...
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