Do BDC dials/reticles work?



  • In response to this thread:
    http://www.sniperforums.com/forum/optics/51907-custom-dials-ballistic-data-hunting.html

    The direct answer to the original question is that inside 500yds with a flat shooting magnum, a calibrated BDC will suffice for most shots on big game in most conditions. Beyond that, the specific conditions and area of operation matter with increasing importance the farther you get out. The proof is in the numbers, which I would recommend you educate yourself on before launching bullets at distances you are unfamiliar with.

    **Consider a 7LRM launching a Berger180 @ 3020fps: **

    28.5in/Hg, 20F, 50%, 10mph@9:00
    500yds - U2.0, L0.7
    1000yds - U6.5, L1.7

    80F (instead of 20F)
    500yds - U1.9, L0.7
    1000yds - U6.2, L1.5

    That's a huge temperature swing that represents the largest swing you can really have when hunting during most big game seasons. As you can see at 500yds, the difference of a 60 degree temperature shift is only going to cause an error of 0.1 mils. That is roughly 1.8 inches at that distance. That is still a hit on a big game animal, without question. At 1000yds however, that error is 0.3 mils which is over 10 inches. At that distance, 10 inches of error, combined with natural shooter error can absolutely turn into a miss fast.

    The distance at which a BDC stops working effectively is a combination of the ballistics of the cartridge/bullet used, target size, conditions, distance, and shooter proficiency. It's very easy to get acceptable results from them out to 500-600yds with most magnums shooting modern bullets. Smaller cartridges with less impressive ballistics will have a tougher time of it.



  • I still don't get why you need a BDC turret. Just because the turret is marked 500 yards, your still dialing the 2.0 up.



  • @norcal_in_az some people can't wrap their head around the concept.

    This is a good idea:



  • @norcal_in_az said:

    I still don't get why you need a BDC turret. Just because the turret is marked 500 yards, your still dialing the 2.0 up.

    BDC is indeed much faster.
    Get range, dial or hold to that range, fire.

    With mils, you need to coorelate that range to a drop chart before dialing/holding.
    Get range, check dope for range, dial or hold that dope, fire.

    Unfortunately the BDC stuff doesn't provide the level of accuracy we need when shooting at very small targets, or targets which are further away than the specific cartridge/bullet's ballistic superiority lasts.



  • I agree with orkan here. BDCs are fast but for the most part are not as accurate as dialing a specific firing solution. I use a BDC on my 270 hunting rifle, and it is much quicker than dialing, and allows good hits but not the same accuracy wise. I trust it to as far as the drop hashes go, but change things like muzzle velocity, DA, temperature and such and the BDC changes just slightly. For example on my 270 the drop hashes in my BDC represent a different distance in the winter than they do in the summer much like the 60 degree temperate change orkan has previously mentioned, which isn't unheard of here in New England. Last Sunday was 80 degrees, this coming Sunday were foretasted to get 4-8 inches of snow which as represented can change the BDC.
    For example the firing solution for a 270 Shooting a 130gr Nosler with a BC of .432 at 3060 on a 76 degree day. This shows the first hash marked at 1.5 MOA as the solution for a 221 yard shot. The farthest hash which is 11 MOA is the solution for a 583 yard shot.
    http://apps.vortexoptics.com/lrbc/#logged-in?basic_id=89615

    The same date but on a 40 degree day shows 1.5 MOA as the solution for a 219 yard shot and 11 MOA as a 572 yard shot.
    http://apps.vortexoptics.com/lrbc/#logged-in?basic_id=89615
    So at 580 yards I need 10.85 minutes on a 76 degree day and 11.27 on a 40 degree day.
    About .5 minutes difference at the same distance.


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