Burris Ballistic Plex Calibration?

TAA

TAA

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I have a couple of 3x9 ballistic plex scopes and really like them. Recently I shot a coues whitetail at 400 yards and I had a hard time with the 9x finding him. I'm wanting to go to a higher power scope like the 4.5-14 or even 6.5-20, leaning more to the 4.5-14.

My question is does anyone know what power the plex is calibrated to? I've been on the website and done a search and cannot find this information. My 3x9 has to be on 9x for the drops to be right.
Thanks
 
Same holds true of almost all balistic reticle scopes the scopes are set to use the reticle at the maximum power of the scope. This does cause some problems in low light where one needs to dial down the power to say 6x to brighten up the scope. There are some alternatives though. Zeiss has several balistic reticles and a balistic calculator on their web site which can be helpful. One fix is a FFP scope like the SWFA 3-9x42 Super Sniper with FFP mil dot reticle where the dots can always be used for known hold over at any power because they are always one mil apart. one mil is 3.6 inches at 100 yds. Mil dots like MOA are measurements of an angle like a piece of pie. Now for the complex part. For you guys who have a second focal plane reticle (reticle looks big all the time doesnt appear to change size). So long as one is using the exact same power all the time one can make notes on what the hold over lines represent. This is easiest at the lowest power of the scope and at the highest power of the scope but it can be done at any power. Lets say I bought a 6-20x50 Zeiss with Z800 reticle. At 20x each of those lines represents something and we just need to know what so we look at their balistic calculator and plug in info on our caliber and bullet then test it on the range. Zeiss will tell you exactly what power matches most closely to your specific caliber and bullet and it may be something like 14.3 X most closely represents a true line 2 is 200 line 3 is 300 etc.
So we go to the range with our 6-20x50 scope and zero it so the crosshair is zeroed at 100 yds. Now lets put the scope on 6x put the crosshair centered on the 200 yd target and shoot a hole in the target and mark it big enough to see from the 200 yd bench and at 6x look what line corresponds to that hole it may be the half way to the first line below center so to test our theory for our next shot we hold over using 6X aiming with the half way to the first line at the 200 yd target and it strikes the X ring proving what point we need to use for hold over at that distance. The first line down that might have represented 200 at 20x may represent 300 or 400 at 6x you just have to test it. This will take work on the range and making notes but it will work for you. The same holds true for any specific power the lines represent something we just need to find out what they represent at that power and then when we return to that power we can use those hold over notes we made.
 
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Originally Posted By: sscoyoteThe 4.5-14x needs to be set to 14x for the advertised stadia subtensions (measurements) to be correct.

Yep. But even then they won't be. Chrony your load, tell Burris velocity and BC of bullet and they can tell you pretty closely what yardage each hash mark should represent........
 
With my Ballistic Plex reticle, I placed an X at the bottom of a piece of cardboard and shot it at 100 yards, then did same for all of the graduations and came up with a "ladder" of the trajectory, the results showed suprising regularity. I then used those measurements and compared them to a ballistic calculator for approximate range estimations. Then just shoot at those ranges to verify. As already stated, you need to use the same power setting to reproduce this in the field.

Last time I had done it was with a superfast 110gr 30 cal load and the 100 yard MPBR was 277 yards, while the 2nd stadia line was 250 zero. Last line was 686 yards. So probably more effective on a heavier bullet.
 
When i calibrate a reticle to the trajectory of my load i always use the optics highest power, no matter what reticle i am using. I then run a ballistics program for my load and test 3 different points along the trajectory, especially x-hair zero. Usually the ballistics program is close. If not i calculate MOA error at each range, then go back to the ballistics program and change BC +/or muzzle velocity to get a closer match to the true trajectory. I then calculate reticle zeros in 25 or 50-yd. increments only. Here's an example. Suppose i have a Ball. Plex reticle on a gun. I know that at the optic's highest power the 2nd and 3rd subtension r 4.5 and 7.5 IPHY respectively. If say my 425 yd. trajectory is 6.2 IPHY below x-hair zero then i subtract 4.5 from 6.2 and that's 1.7 IPHY. Now there is 3.0 IPHY between #2 and 3. So if i divide 1.7 by 3.0 that's 0.6. Now the entry on my range sticker for that range is 2.6. Now do the same for windage, and u'll have an interpolative grid established that will allow for the most accurate system of reference for that reticle vs. trajectory.

There is some viability to adjusting subtension by adjusting the power in 2nd focal plane reticles, and that may be a better way to go. All one needs do is calculate and establish x-hair zero. Now shoot the zeros at 300, 400 and 500 yds.--even 600 if the reticle goes that far. Now calculate the drop at all the ranges in MOA, and mark each MOA zero on the 100 yd. tgt. Look at it with your reticle and adjust the power until the stadia lines line up as close as possible paying particular attention to the longer ranges. That's the "abbreviated intuitive 2nd focal plane reticle zeroing system"...sort of.

Burris has done a great job of describing the systems in the above noted links.
 


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