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#29
02-05-2010, 06:41 PM
 Silver Member Join Date: Apr 2009 Location: Pocatello, ID Posts: 352

Very true,
What are the bennifits of the fixed power scope over the variable? Do you use one? I know that bushnell make a heck of a fixed power taticle scope in their elite 3200. Any thoughts?

Darrin
#30
02-06-2010, 10:19 AM
 Silver Member Join Date: Dec 2009 Posts: 104

After rereading the warranty 1 yr wouldn't cut it. The scale used for range estimation is in MOA that is why the formula is height/width in inches add 2 zeros divided by the minutes = distance to target.
It's my understanding that in order to range a target in mills you must know the height in meters/yards x 1000/ by mils. If you use inches for your target X 27.8 for yds and 25.4 for meters get's divided by the mils read = your distance. Is the USMC mil scale a different formula? I know they use true 6283 mils for a degree instead of the 6400 the army uses????
The Horus vision grid use mils for holdover and windage. So are the clicks at .1 mil (.36moa)
My mistake for the confusion
To answer the fixed power scope question. A fixed power ranging reticle will subtend the same amount at any range. You just need to know your target size,and the apporpriate formula for your reticle. This is why a first focal plane reticle in a variable power is used in most military optics.
Here is the biggest problem with 2ndFP mil dots. If you have heavy mirage due to barrel heat or high temps, shooting from heated buildings. Using the scale at max power may not be possible. Just as a laser may be inoperable.
If you were to take that same 2ndFP mil-dot and calibrate target sizes from 100 yds/meters then it can be more useful, and much faster.. Say your target is 18"(5mils) At 100 yds/meters 18" is 5mils on 3 power. Now take your variable power ring and dial in the power till it subtends 5 mills. If you started at 3X and to get to 5 mils for your 18" target you moved to 10.33X You can safely dial in your dope for 733 yds 10.33-3=733yds. If you want meters you need to calibrate you mil scale at 100 meters. How many mils subtends X amount of inches on the lowest power at 100 meters.
Taking that same 18"(5 mils) we now dial in the power ring and see we have 9.5 power 9.5-3=650 meters. Use your drop chart dial in the dope needed.
Point is you can use whatever scale in your scope you have. The only thing you need to do is calibrate what the subtensions are at the lowest setting at 100 yds/meters Even a plain duplex reticle can be used it just needs some practice. Is it optimal, no but it can be used effectively with practice.
#31
02-06-2010, 10:24 AM
 Junior Member Join Date: Jan 2010 Posts: 15

usmc formula is the same.
#32
02-06-2010, 03:20 PM
 Platinum Member Join Date: Feb 2003 Location: Pueblo, CO Posts: 1,138

All reticle-rangefinding is based on the most basic form of the mil-dot mil-ranging formula, from simple plex to Ballistic plex--it's all the same equation just various units. I always use my multi-stadia reticles for rangefinding at the optic's highest power.

Here's the equation that i use--

tgt. size (") x range of reticle subtension measurement (usually 100 yds.) / subtension (") / quantity of "gap" tgt. occupies (decimal equivalent) = range (yds.)

Here's a couple pics to show how it works for a mil-dot that's calibrated for a power lower then the highest (12), and then mil-ranged at the highest power (18) where the mil-dot subtension is now 2.38 inch per hundred yds.--

tgt. size-12", range = 300 yds.

1st pic) 12 x 100 / 3.6 / 1.15 (maybe?) = 290 yds.

2nd pic) 1200/2.38/1.7 (edge of tgt. is below x-hair slightly) = 296

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