Leupold Gurus

[Varmint Hunter]

I have a question that only one of you Leupold Gurus can answer. /ubbthreads/images/graemlins/smile.gif

I had a Leupold "Varmint" ballistic reticle installed in my 6.5x20 Leupold It can be seen here if you scroll to the bottom of the page (biggame reticle is on top) look here .

The reticle has 10mph & 20mph windage dots. Naturally, that would be highly dependant on bullet BC and velocity. I will be shooting a 162gr A-Max (BC .625) @ 3,100 ft/sec.

What wil the windage dots actually represent with my load. I'd like to make this a quizz but I don't know the answer myself. /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/confused.gif /ubbthreads/images/graemlins/grin.gif

VH

 

[Buffalobob]

Varmint hunter


Funny enough I went to the Hornady manual but they stop at a BC of 0.56 and do not give a calculation for a BC of .625 so I went over to 6mmBR.com and used their ballistic calculator.

The first number is the range, the second number is the distance in inches to the left or right of the dot and the third is the drift of the Amax in inches with a 10 mph wind

yds-----reticle---Amax drift @ 10mph
200-----3.71"----1.9"

300-----8.98"-----4.3"

400-----17.13"----7.9"

500-----25.87"----12.6"

I conclude that this reticle windage is designed for a BC of about 0.3 or 0.35

For your bullets the 10 mph dots would actually be 20 mph and the 20 mph would be forty miles per hour.

What it means is that you can only shoot during tornados and hurricanes. That should be interesting.

An option would be to develop a little cheat sheet to tape to your stock. that would only use certain ones of the dots.

For example the 200 bar is good for 300 and the 300 bar is good for 400yd windage and the 400 bar is good for 600 yds (18.7 inches drift) and the 500 bar is good for 700 yd windage(26.2 inches @ 10 mph)



I think the expert on these reticles is SScoyote so you might want to double check with him.

 

[Varmint Hunter]

buffalobob,

I knew one of you guys would figure this out. /ubbthreads/images/graemlins/cool.gif Thanks

Actually, this load would be flat enough that it may very well work out zeroing the rifle @ 300yds with the main horizontal crosshair and use the lower crosshair for 400yds rather than 300yds. Interesting suggestion.

Looks like the windage dots won't be very useful unless that Wyoming wind is a bit stronger than I thought. /ubbthreads/images/graemlins/grin.gif

VH

 

[sscoyote]

Thks. Bob-- appreciate the vote of confidence.

VH-- i also have 1 of those VH reticles also on a Savage Striker 243 WSSM, and the windage system is about 1/2 the rated windage values. Borrowing the info Bob put up on the drift figures here's how i do it. 1st off i convert the reticle and windage figures to MOA as follows from Bob's calcs.--

yds.----- reticle----- Amax drift @ 10 mph

200-------1.77 MOA----- .9 MOA

300-------2.85----------1.4

400-------4.1-----------1.9

500-------5.5-----------2.4

Now divide the MOA windage figures by their respective reticle subtensions in MOA to reference windage quickly in tenths of each subtension, like this--

200 = .9/1.77 = .5 of the total "200 yd." stadia unit

300 = 1.4/2.85 = .5 "300 yd." stadia unit

400 = 1.9/4.1 = .5

500 = .4

Should be easy enuf to reference just like the mil-dot guys use for windage holdoffs with a chart or range sticker on the scope. I also use the lower post as a zero @ 9.35 MOA, AND I ALSO PUT THE 1/2 WAY POINT BETWEEN EACH STADIA FOR ZEROING AND WINDAGE on the sticker using the calc'd windage stadia subtension above as a reference.

Now while i was calculating this stuff i happened to notice something interesting. There may be an error in the posted 500 yd. MOA calcs. on the Leupold website here--
http://www.leupold.com/products/Info_Ballistic_Aiming_System.htm

If u notice the 500 yd. windage is displayed as 25.87"-- which should calculate to 4.9 MOA (25.87/5/1.05) not 5.49 as they have calculated--IF MY CALCS. ARE CORRECT. If my calcs actually r correct (possibly a big IF) it looks like all their 500 yd. stuff is off some. Interesting, any comments?????