View Full Version : Doping question/ MRADS
February 20, 2013, 07:59 PM
Can anyone please check my math on this equation and help me with doping my MRAD .1click scope?
Rifle, Remington 700 SPS Tact AAC-SP
Scope: Viper PST 6-24x50 MRAD Retical
Load: 308 Winchester, AMAX Match, 168 GR, 2700 fp (HOrnady)
Alititude: Sea Level
Bullet drop: -378in (using JBM Calculator)
That would be close to 37.837 MOA???
Converted to MILs or MRADS would be 10.51???
First time using scope with MRAD .1 turrets
Each Rotation is 5MRADs
if 1 click of elevation is .1 MRAD
Would that be 100.5 clicks of elevation???
February 20, 2013, 08:02 PM
I apologize, i meant 105 clicks of elevation, not 100.5
February 22, 2013, 10:01 AM
Not sure if you're looking to convert 105 .1 mil clicks to moa or inches.
105 would be 10.5 mils.
1 mil = 3.438 moa
or 1 mil = 3.6 inches.
So it would either be 10.5 * 3.438 = 36.099 MOA
or 10.5 * 3.6 = 37.8 inches.
A MOA is 1.047 inches so to check the math 36.099 * 1.047 = 37.7956 or 37.8 inches if you round up.
March 3, 2013, 03:15 PM
First off, it depends on what standard you want to use for MOA values. In the late 19th century, it was 1/3600th of the range. At 100 yards, that's 1 inch; 10 inches at 1000 yards.
That all was based on USA smallbore and high power rifle target's scoring rings being spaced in exact inches. Virtually all the scope makers used that standard for their externally adjusted scopes. With a 7.2" mount spacing and the knobs 40 tpi threads and 50 clicks per turn, that moved the adjustment exactly .0005" per click, .002" for 4 clicks. 4 clicks equals one MOA or inches per hundred yards; 7.2/3600=.002. Aperture sights on target rifles with a 24" barrel typically had a 30 inch sight radius. 30/3600=.008333" or exactly what the 40 tpi lead screws on those sights move the aperture in 1/3 turn; three MOA per turn.
Along comes some engineers in the 1970's and 1980's and their calculators said there was 1.0472" per hundred yards for one minute of angle; their high priced trigonometry function calculators proved it. So what. It's been the "shooting standard" of 1 inch per hundred yards for centuries. But now it's confusing 'cause scope makers use both.
To say nothing of the four different world standards for a "mil" on this planet:
* 1⁄6400 of a circle in NATO countries.
* 1⁄6283.185 The “real” trigonometric unit of angular measurement of a circle in use by most telescopic sight manufacturers using (stadiametric) rangefinding in reticles.
* 1⁄6000 of a circle in the former Soviet Union and Finland (Finland phasing out the standard in favour of the NATO standard).
* 1⁄6300 of a circle in Sweden. The Swedish term for this is streck, literally "line". Sweden (and Finland) have not been part of NATO nor the Warsaw Pact. Note however that Sweden has changed its map grid systems and angular measurement to those used by NATO, so the "streck" measurement is obsolete.
Then there's the mechanics of the scope that move the tube with lenses that changes the target image position on the reticule. Whatever math they used typically only is close to their spec.
One should accurately measure their scope's adjustments on a ruler at 100 yards. Line up the scope very solid so it is well fixed in posision, then move one adjustment 40 clicks. If it's a shooters MOA adjustment, then the reticule had better move exactly 10 inches for 1/4 MOA clicks (or 5 inches if done at 50 yards) 10.472" if its a trig MOA scope. But it'll probably be someplace between 1 and 3 percent off. Darned few internally adjusted scopes are exact.
AT 999 yards, one shooter's MOA is 9.99 inches; one trig MOA is 10.4615 inches. Specs say its 1/10th mrad, but with its first focal plane reticule, it may be off as the front lens that focuses the target image there may not be exact for specs; most lenses vary a few percentage points. Which is why I suggest carefully measuring yours to see what it actually does.
vBulletin® v3.8.7, Copyright ©2000-2014, vBulletin Solutions, Inc.