Posted: 1/3/2012 3:00:38 PM EDT
[Last Edit: Apple_Tech][Edited]
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I have a millet TRS-1 4-16 power.
At 10x it is on with 1 mil = 3.6" but at 16x it is 1 mil = 2.5" I'm trying to figure out a formula to convert my dope chart ( i have both drop in inches and mils). I want to have a quick hold over sheet for my 16x Thanks! EDIT: Think i figured it out. plus you could use to figure out any mil holdover. This only works w/ second focal scopes and if you know the value (inches @ 100yds) at a given power. Drop (inches) / ((Range / 100)x Y) Y= Scope value at given power. ie: 10x = 3.6"@100yds, or 16x = 2.5" @100yds Example: 400 yards, 30.4" drop Scope on 10x 30.4 / ((400/100)x 3.6) = 2.1 Mils Scope on 16x 30.4 / ((400/100)x 2.5) = 3 Mils |
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Wonder if you don't have a similar problem that I am running into? I have recently come across 2 Millett 4-16x50 TRS-1 scopes that some of my shooting buddies are using where the reticle reading/calibration is off.
With both scopes set at Max/16x, I ranged a 48" object at 200 yards which should have given me a reading of 6.6 MILS in the reticle. On one scope I was getting 7.0 MILs and on the other I was getting 7.1 MILs. I also ranged a 6" object at 100 yards which should have given me a reading of 1.7 MILs, but I got 2 MILs with both of the scopes. I contacted Millett Customer Service, and they said to send them back, something was most likely off with the magnification settings. I have not gotten any additional information back yet. I am not sure if the problem is with the reticle dimensions, or with the magnification power settings? In terms of the MIL math, Most common numbers are 1 MIL = 3.6", though for the ease of doing math and making scope adjustments, some people will use 1 MIL = 3.5". In terms of true angular measurements, 1 MOA = 1.047" @ 100 yards, and 1 MIL = 3.438 MOA. In terms of using a Second Focal Plane Scope for ranging on a power other than the factory setting, I.E. your SFP scope is setup to range at 20x, but you are on 10x and you want to use the reticle to range or hold. Formula: Desired Power / Factory Set Power = Mod Factor Reticle Reading / Mod Factor = Actual Reticle Reading. So 10x / 20x = 0.5, take whatever reticle read you have and divide it by 0.5 . Some Examples using the Mod Factor of 0.5 from above: You range an object and get 2 MILs, but since you are not on the magnification power specified by the factory, you take your reading of 2 MILs / 0.5 = 4 Mils. So you would actually plug the 4 MILs into your ranging formula. Your dope indicates a 14 MOA elevation adjustment. You want to hold that in your reticle. Depending on whether you want to use 1 MIL = 3.5 or 3.6 MOA, I am going to use 3.5 MOA because the margin of error is negligible and it makes the math quicker / easier. So 14 MOA / 3.5 = 4 MIL hold in the reticle if you had it set on the magnification power specified by the factory. Since you do not, use the Mod Factor from above, so 4 MILs / 0.5 = 8 MIL hold in the reticle. If you do these math conversions ahead of time, and carry that data with you (in your head or on paper), you can refer to it and quickly employ a SFP scope on numerous magnification settings. Hopefully that all makes sense and helps, M Richardson |
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Recently I've worked on the same issue.
There is another concern: the zeroing at different magnification may shifts, i.e. at 12X it is zeroed at the cross hair. Now changing to 24X, using the cross hair the POI and POA may not be the same. Of course, it can be calibrated out by test firing. |