Finding drop data with handloads?

Discussion in 'Long Range Hunting & Shooting' started by Brydawg512, Mar 20, 2019.


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  1. Brydawg512

    Brydawg512 Well-Known Member

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    Hello all,

    The rifle is an older (probably 80s) Winchester M70 chambered in 7mm rem mag, completely stock. I am in the process of buying my first set reloading equipment to load for this rifle. I have a few questions regarding this.

    I have a new Vortex Viper PST that I will be mounting on this rifle. First, before loading my own rounds, should I "rough" sight this scope in with factory rounds before loading my own rounds? I am having a few hiccups here as I am unsure how I make sure that when I am testing the loads that it isn't a poor load, when it could be the fault of the scope or rifle.

    It's difficult to describe what my issue is online. My biggest problem is how do I ensure the rifle isn't causing performance issues (barrel, not floated/bedded, trigger, etc.) over the round being the culprit? And again, how do I ensure I am sighted when I am testing these new handloads?

    Sorry, very new to this all. Thanks in advance.
     
  2. DUSTY NOGGIN

    DUSTY NOGGIN Well-Known Member

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    yes , at least to find paper
    shoot first find out if scope or rifle second ..
    point of impact will change , even between powder charges of your load test ... usually i dont see it move more that about 2-3 inches though . just find paper , always aim center . if you find a tight group load, just adjust your scope for that POI , if you are consistent with your loading it will keep landing on that same spot ... try diamond shape targets
     
  3. dfanonymous

    dfanonymous Well-Known Member

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    So you’re talking about sighting in and not actual finding drops data at different distance? Just to clarify..
     
  4. Brydawg512

    Brydawg512 Well-Known Member

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    Ok, so you are saying that it is the grouping size that matters, not the point of impact (which would make sense)? Also the point of impact will change in between loads because of velocity changes, correct?

    Now, my question is how do I know if the grouping size, if poor, is a result of the load or the rifle?
     
  5. Brydawg512

    Brydawg512 Well-Known Member

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    My apologies, I completely neglected to write that part. Yes, so once I have a load determined, how do I determine my drop data? Do I use the BC of the bullet used in conjunction with a chronograph for the velocity as my input variables on a rough drop data program/website?
     
  6. dfanonymous

    dfanonymous Well-Known Member

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    Um yeah, you can. It’s why it’s important that your loads are as CONSISTENT as you can get them.

    I wouldn’t worry the super far stuff until you are satisfied with the close range work.

    Another method you can do is wright down the drop at known distances with the atmospherics/da of that day, then go true the numbers out by tweaking mv and a wee little of bc to make those numbers match your drop in moa, mils or whatever you are using in your software. Using a reliable chronograph and starting with a published bc iwill probably be the best way to start. Truing is more of a thing that negates other errors that can’t be controlled without truing.
     
  7. Brydawg512

    Brydawg512 Well-Known Member

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    Ok, great. Thank you very much for the help.
     
  8. DUSTY NOGGIN

    DUSTY NOGGIN Well-Known Member

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    velocity mostly vertical chance and muzzle vibration vertical and horizontile

    group size . would be the biggest indicator .. if you can only shoot 2" groups feeling good about all shots and certain parallax is not an issue. then dig into rifle bedding and loose scope mounts
     
  9. CVCOBRA1

    CVCOBRA1 Well-Known Member

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    You stated in another thread that this was your grandfathers gun. Have put much trigger time behind this rifle? I suggest you fire different brands of factory ammo to get the feel of your gun. To start with, you need a good crisp trigger pull in at least the three pound range or you will be fighting a battle all the way.