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Thread: Just Starting in Precision Rifle

  1. #11
    Join Date
    Oct 2012
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    Strelok pro has a trajectory validation feature. I don't have a chrono, so I used this feature to true my velocity. It works by applying your actual drop at distance to adjust either your velocity or BC, your choice.

    I chose velocity because my 20" barrel length is a bit less common.

    In the App, press the icon at the bottom right of the main screen for your setup. It is an arc hitting a target with an up/down arrow.

    Plug in your actual drop and it shows you the velocity (or BC) to use.

    I use the ballistic X app to accurately measure drop from the center of the group being measured.

    After doing this. I was dead on at 200 and 300, but I don't have access to a longer range yet to fully test.

    Sent from my SM-G960U using Tapatalk

  2. #12
    Join Date
    Aug 2007
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    Quote Originally Posted by Send it... View Post
    As Jacob at Rifles Only always says believe the bullet. What is the actual drop and drift? Get that and truing a calculator gets a lot easier.

    I’d much rather get hard dope at distance and record that. Thats what the bullet is actually doing. Knowing that your setup takes 2.6 mils at a certain distance and 5.4 at another is confidence inspiring. I’ll create a drop card of hard dope, shot on paper first.

    Then you can true your ballistic calculator to match what your bullet is doing. Velocity first, then BC works for me.

    Best of luck.
    I'd wager most PRS type shooters who shoot at lots of different ranges in lots of conditions, never have to true their calculator. A combination of a good calculator, litz' BC, and velocity from either magnetospeed or labradar, will pretty much get you on target. For me, the only time i needed to true was when I was goofing with something, like i shot pointed bullets for a year and that changed the BC slightly. earlier, i used some calculators like Field Firing Solutions on a Nomad, and it required truing.

    however, if you are going to true, this is the way (like sendit said above, velocity first then BC):
    1. start with published BC in your calc. shoot at 300-400 yards on a tall target with your 100 yard zero dialed on scope. put a POA like a small shootnsee at the top, and let the bullet fall and hit the target. be sure you know the precise distance with a LRF.
    2. measure the distance from POA to POI on the target. Use that to calculate your actual muzzle velocity.
    3. enter your actual muzzle velocity in your calculator and get a new solution. confirm with hits if desired.
    4. now calculate how far away the transonic zone is, and place a target shortly before that. e.g. if your bullet goes transonic at 1200 yards, put a target around 1000-1100.
    5. shoot at that target and adjust your BC until the calculator gives you a solution that matches what you actually needed to dial on the scope to hit the target.
    6. confirm calculator is giving you good data by shooting multiple distances.

    note: a single BC, even g7, will not give you a great solution at all distances because it's velocity dependent. if the vast majority of your shooting is going to be limited to say, 700 yards, then use that to true your BC instead of the transonic zone. It will give you better data up close, but way worse at distance. (this is kinda similar to a 50/200 zero on ARs. if you zero at 200, you'll be close at 50. if you zero at 50, you could be quite a ways off at 200)

    hth
    Last edited by taliv; 03-25-21 at 16:45.

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