Speed Drop - Witchcraft turns your Mil reticle to a BDC

Tim

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This is some serious voodoo stuff that makes sense when you work out the math. I've run the numbers on 3 different rifles/loads and it all works out.

What if your Mil hash reticle lined up for 2 Mil = 200 yds, 3mil = 300yds, 4mil = 400 yds, and so on out to about 650/700yds? No more "1.4 mil for 200" or "5.6mil at 600" etc. ? Having the mil stadia line up with yardage - essentially a BDC - FOR ANY LOAD would be so much more intuitive.

This is appropriate for DMR, 3-Gun, Hunting where your targets tend to have a decent amount of leeway. IOW, not for PRS or true precision. This method essentially gets you within +/- 0.2mil between ~200-6/700 yards.

Here's the short version (too late?).

- Load all of your data into your favorite ballistics calculator (I did this with a Kestrel and Applied Ballistics)
- Zero your scope for 100 yards (feel free to sub meters anywhere I use yards)
- Calc your drops at various distances like 3, 4, 5, 600 yards.
- Then....subtract the adjustment from the "hundreds" place to get your speed drop value. It's easier to illustrate than describe. All of the following uses my data for a 6.5CM.

YardsMil AdjustMathSpeed Drop (Mil)
3000.93 - 0.9 =2.1
4001.74 - 1.7 =2.3
5002.65 - 2.6 =2.4
6003.66 - 3.6 =2.4
7004.77 - 4.7 =2.3


Notice a trend? The "speed drop" works out to ~2.3 Mil +/- a minor amount.

So, what do we DO with this info? Easy peasy....dial your elevation UNDER zero to match the Speed Drop. et viola! Your Mil reticle is now a BDC. At 300 yards, your 3Mil stadia is +/- 0.2 MIl. 450 yard shot? hold 4.5 mil in your reticle.

From my 100 yard zero, I'll dial DOWN 2.3 mil.

The speed drop doesn't translate well for close in shots (inside 200 for example), you can either dial back to zero for those engagements, or learn to hold over for those shots. In my mind, this is a HUGE improvement for longer range stages. I don't need to remember or scribble on a cheat sheet all of the Mil adjustments. As long as I know the range, I have my reticle for hold overs.

Even if you don't actually adjust your turret down to the speed drop value, knowing this number can translate bigly on the fly. "It's a 700 yard target....7 mius 2.3 is 4.7....hold 4.7mil...bang"




 
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That’s great info, and one I’ve had bookmarked for quite a while. However, the ‘hide is tending towards more precision shooting over longer distance.

What I describe above is the “good enough for large targets at mid range” answer when you are happy to trade a bit of precision in favor of speed. Again, games and hunting.
 
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Worked with 3-4 different rifles (mine and others') yesterday to set this up. This voodoo works!

On my 11.5" AR I dialed 'down' 1.6 mil. Proceeded to go 1:1 out to 600 using mil hash reticle. If you have a MIL based reticle and want to turn it into a BDC, this method is the bomb. Again, not for precision work but perfect for DMR and hunting.
 
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