Thoughts on BDC's

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Guest, Nov 25, 2004.

  1. Guest

    Guest Guest

    Thoughts on BDC\'s

    Since this sorta was a controversial topic I thought I'd share my thoughts and some realities of this is it applies to the LR hunting aspect. I feel some of the information prior to this was misleading. There a numerous people here who are interested in learnin and aquiring information so I thought I'd share my ideas and information on BDC's

    The pros

    easy "doping" if you know your rifles performance.
    Simplicity in the field for the inexperienced.
    Possibly a good tool for the novice.

    cons...

    while in reality they appear to do what they are intended for it really could cause problems.
    These BDC's are made for a rifles spacific performance with a specific bullet, specific powder, specific primer. That in itself spawns numerous problems.

    I can show drop charts with varying conditions that will show impacts with enough variation to cause a miss or wounded animal. Based on atmospheric conditions alone. But consider these variables as well.

    Your perfect powder,primer,bullet combo works really well in your back yard. But you travel to a different elevation or climate to hunt.
    well your powder perfromance may not be the same in your hunting area... maybe you have an enormous pressure increase or decrease... now what? Couple that with the bullet performance at a the changed altitude, and atmosphereic conditions... you have a recipe for disaster.
    Now let say you have a very stable combination of powder,bullet,primer. Great, you have used your rifle sucessfully for a season or two.. but any good LR hunter fires many rounds in the off season to keep in tune and sharp. Most LR hunters shoot calibers that may be pretty hard on barrels.. now you begin to erode your lands and rifling... that translates into lower velocities or deminished accuracy... ( lower impact points) NOW what? well options.. rebarrel, order a new BDC, or work up a new load to match your BDC. Keep in mind you new load work up continues to wear your lands and rifling.

    In my opinion while the information on the previous post seemed flawless and reliable it truly can cause numerous problems if the rifle owner doesn't fully understand the logistics. These BDC's may seem like a fix all but again, in my opinion, they may cause more problems than they fix...

    My solution is shoot and shoot often, keep notes and learn your rifle. AS your rifle performance changes you will be aware and can accordingly use your reticle or adjust your clicks.

    again, just my view and opinion.... hope this helps someone...
     
  2. cdmorten

    cdmorten Well-Known Member

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    Re: Thoughts on BDC\'s

    I'm a fan of BDCs. The BDC on my M3 works perfectly when conditions are perfect, (perfect being defined as the same conditions in which I sighted in my rifle). Throw in a 40 degree drop in temp and you may have to come up an MOA.

    There's no substitute for knowing how your rifle shoots at different temperatures and humidity rates. I keep a log book for that reason. The book may sound like a pain, but I've gathered some good knowledge over the years. The BDC's are going to give you solid hits within 400M. Outside of that, atmospheric and environmental factors can start to come into play and you may have to deviate from the BDC.

    As for the ammo. I don't reload. I use either Black Hills Match grade or Federal Match grade and they both track identically with my BDC.
     

  3. Brent

    Brent Well-Known Member

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    Re: Thoughts on BDC\'s

    I use one.

    It's calibrated in MOA, and thus offers an advantage over moast others... instant adaptability.

    I fully understand where Ric is coming from, and have to say that he is just well tuned into the finer points of LR precision that many have yet to even become aware of... a clear understanding is just the concern, I'm sure. Simple it can be, but simple it is always not.

    And believe me, here, Ric only touches on the heap of variables that can affect POI shift. Beyond 500 yards it becomes necessary to understand most of them, at the very least to know that they exist.
     
  4. Guest

    Guest Guest

    Re: Thoughts on BDC\'s

    Amen to that... but I don't worry about alot of them just refer to notes after 600 yards or so...

    The BDC are great for rifles in the 308 caliber, 260 caliber.. ones that are easy on the rifling and lands... The high pressure, fast, barrel burners create lotsa problem for BDC's...
     
  5. Mysticplayer

    Mysticplayer Writers Guild

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    Re: Thoughts on BDC\'s

    Within 400m and fast flat shooters, why bother with scope adjustment at all?

    Fine adjustments become a necessity further out where most of us play. Here, all the variations in weather, temp and load will drive you nuts if you work only with a BDC turrent.

    Practise lots in different weather. Use powders that are stable. Keep lots of notes.

    Jerry
     
  6. DMCI

    DMCI Well-Known Member

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    Re: Thoughts on BDC\'s

    This business of BDCs, Ballistics Calculators, Weather meters, etc. are where I have been spending most of my rifle hobby time lately.

    Couple of salient points:

    1. Hunters (Large Game)

    If you shoot/hunt large game only, then by all means take the Weatherby System. Large case, Premium Hunting bullet, High velocity, Flat shooting.

    Barrel wear is not an issue, because you don't fire that many rounds in a year. Maybe 1 box at the most?

    Hunting scope is fine, because these things are typically point blank or in the kill zone out to over 400 yards for large game. Many hunters have strict ethical rules about maximum range shots, etc.

    2. Tactical Shooters

    BDCs work well on tactical targets out to just under 1000 yards. Again these targets are fairly large. It appears that most non-military shooters engagement ranges are well under 200 yards, so in many cases only minor elevation and windage adjustments are necessary for this application.

    3. Target shooters

    Target shooters can win consistently if they can shoot into .5 moa under all conditions. They have sighters, known distances, and other features that simplify the problem for them.

    4. The rest of us.

    Shooting small targets at short to medium range, and medium targets at extreme range in variable conditions and distances.

    Tactical contests and Varmint hunting fall into this category.

    Barometric pressure, Ambient temperature, Wind velocity and direction, Barometric Pressure, along with distance to the target all play an important part in this. Knowledge of the firearm's performance under given initial condition are important as well, as every combination of load, barrel length, bullet, etc. have a significant effect on point of impact.

    So what do I do.

    Equipment as follows:

    Horus Ballistics Program/Palm
    Oehler Chronometer
    Kestrel 4000
    Leica 1200 RF
    Redding Micrometer Sizing and Seating Dies

    Berger, Lapua and Sierra Target Bullets

    Custom Target Rifle and Scope.

    This whole learning process is a lot of fun and while not perfect, answers a lot of questions.

    Comments on BDCs

    They basically allow the owner to write his come up chart on the knob, for a given set of initial condition. As state in earlier posts, a great solution as long as initial conditions don't change.

    A better solution is to take field measurements to adjust initial conditions, and write or print a come up chart for that day. Not perfect, but not bad.

    Tons more stuff, but fingers are getting tired. [​IMG]

    [​IMG]
     
  7. Guest

    Guest Guest

    Re: Thoughts on BDC\'s

    Brent, DMCI

    Thank God someone else can see what I am saying!!!