Converting m.o.a. to inches

Originally Posted By: sscoyoteThere are 1.0472" in 1 MOA, so-- 20/4/1.0472=4.77MOA # I like to use the mil-ranging formula though for almost all of my calculations since it defines not only rangefinding with a reticle or turret system but also downrange zeroing as well, and i only have to memorize 1 formula for just about everything.-- # 20 x 100 / 1.0472 / X = 400 (actually the same as the formula above just rearranged and simplified) # X=4.77 MOA

Im building ballistic tables for my several new scopes. My most recent acquisition is Primary Arms 1-6x24 ACSS - HF, which I like to call Dead Hold reticle. Yes I know, this is like 9 year old post, but I found this cherry and it could be important. It is a fresh approach for me. I wouldnt know how much interest there is in 762x39 but any hog hunter probably is. This here ACSS - HF reticle is tailor made for the 300 Blackout / 762x 39. Primary Arms is tailoring BDC reticles for specific firearms. Ive another tailored for 308 WIN. HF actually stands for Hold Fast.

Ive yet to get Primary Arms to answer my inquiry as to what MOA values this HF reticle with 300-600 yard hash marks is tuned to (etched in glass). Scope manufacturers loosely call the reference pamphlets as a Manual. Like the majority, Primary Arms didnt spare any extra minutes putting together their pamphlet. Now Nikko Stirling puts together a more indepth pamphlet for their Diamond 4-14x50. And this jewel of information has allowed me to tabulate BDC for it as well.

There arent too many ammo sorts for the 762x39 but enough to have a tight awareness of inches to MOA conversion. Such as the 154 grain thumper. Its snot going to line up with this new tailored scope unless I know the MOA to inches hold over for the 154 versus the usual vanilla or chocolate grain flavors. Ize got to construct my Dope cards and I have to start with MOA.

While its old stuff, its news to me. Thank you for sharing.
 
https://www.primaryarms.com/pa-1-6x24mm-...2-reticle-black

The reticle top of the chevron if zero is at 50 yds the underneath part shows 200 yds top of the post below that shows 300 and marks below for 400 500 600 thats with 124 gr ammo in either 7.62x30 or 300 Blackout.

https://www.jbmballistics.com/cgi-bin/jbmtraj_drift-5.1.cgi Balistic Calculator

Your 154 gr "thumper" in 7.62x39 should be running a tad slower than a 124 gr and the result will be that it looses elevation a little sooner than its faster brother. Use the Balistic Calculator above to run a chart for both the 124 gr and the 154 gr and you will know how much difference there is at the distances you will be working at. Then test it on the range to be sure what you are getting.
 
Or learn to get within 300 yards and hold on fur. No math, no fancy reticles, no remembering to return to zero, no cumbersome turrets sticking up, what's not to like.
 
Originally Posted By: AWSOr learn to get within 300 yards and hold on fur. No math, no fancy reticles, no remembering to return to zero, no cumbersome turrets sticking up, what's not to like.

nominate for best answer. ^^^^^^^^^
 
Originally Posted By: SlickerThanSnotOriginally Posted By: AWSOr learn to get within 300 yards and hold on fur. No math, no fancy reticles, no remembering to return to zero, no cumbersome turrets sticking up, what's not to like.

nominate for best answer. ^^^^^^^^^

And I will second that nomination.
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I've had just as much fun applying math in the field than any other type of hunting/shooting I've ever done. The two most fun concepts are--

1) Subtension is inversely proportional to magnification in 2nd focal plane scopes, and-

2) The mil-ranging formula defines rangefinding with any 2 points at one distance relative to any other 2 points at another distance, from mil-dots to archery sight pins and anything in between. It also defines downrange zeroing too as stated above.

Here's one example-- a number of years ago a buddy wanted to know the size of a target was that we were shooting at at 1000 yds. Nobody knew so I thought to measure it with a buddies mil-dot scope--problem was we didn't know what power the scope was setup for. But we had a target of known dimension at 500 yds. so we reversed milled the subtension on that target at the optic's highest power, then remilled the 1000-yd. tgt. and reverse-milled the tgt. size since we already knew the range, and the calc. was within .3" of the tgts. true dimension. That was just as fun (for me) as any shot I've ever made, or stalk really.
 
youtube.com


My rifle scope dials are 1/4 moa/click, not inches. Figuring the MOA for a different range then dial in the MOA change. MOA is an angular measurement and you use Trig to calculate the new MOA at a different range that from where your scope is zeroed at. MOA does not change with different distances as it's an angular measurement that always stays the same. Now the bullet drop changes with distance and you must figure out your bullet drop at different ranges and then calculate the MOA changes to bring the bullet back up to the target and compensate for the bullet drop beyond and before the zero range. But this video makes it very easy to do that if you shoot your gun and learn the amount of bullet drop beyond where you zero the rifle.

Check out this YouTube video from the NSSF.





Originally Posted By: quarterboredDude...

It totally depends on the range that you're figuring the 27.9".

If it needs to come up 28" for a 300-yard compensation... then you'd need to dial in 37 of the 1/4" clicks (+9.25" @ 100yds)... because every 4 "clicks" equals a 3" elevation correction at 300 yards.

If it needs to come up 28" for a 400-yard compensation... then you'd need to dial in 28 of the 1/4" clicks (+7" @ 100 yards)... because every 4 "clicks" equals a 4" elevation correction at 400 yards.

If your scope is set-up for 1/4" clicks (or 1/2"... or 1/8"... etc.)... then you need to figure your drop out in INCHES... "MOA" means nothing to you... even though they're nearly interchangeable.

This whole system is MUCH easier to think about in whole inches rather than "clicks". From a 200 yard zero it's sooooo much simpler to just have a chart that says:

.25-06 Rem, 115 VLD @ 3150, 5000' Ele. (or whatever you're shooting)
200 = 0
300 = +2"
350 = +3"
400 = +4"
450 = +5.25"
500 = +6.5"
550 = +7.75"
600 = +9"
650 = +10.5"
700 = +12"
etc...

Then... just look at the dial on the scope... and turn it to the corresponding number... and WHAMMY. After the shot, dial back to your "0"... and you're ready to do it all again. youtube
 
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What you need to know is your bullet drop for your gun/ammo and there is really no need to calculate the MOA as it can be figure easily in your head.

One MOA Equals=
1" at 100 yards
2" at 200 yards
3" at 300 yards
4" at 400 yards
5" at 500 yards
6" at 600 yards

If your bullet drops 36" at 400 yards then divide 4"/moa into 36 and that equals 9 MOA. So dial your scope up 9MOA and you should be on target at 400 yards.
Note: this is with a 100 yard Zero for your scope and using a hypothetical bullet/gun combination. I made up the 36" bullet drop at 400 yards just for an example of how to figure out how many MOA you need to dial up the scope to hit the target at the theoretical 400 yards target.

All this can be done in your head easily.

And you can use a First Focal Plane Milrad target reticle to calculate the distance if you know the size of something down range. See the NSSF videos to see how to calculate the range using mil dots in a reticle.
 
Originally Posted By: yoteaddictI thought I saw a chart in a previos link on converting m.o.a. to inches. Example = 20 inches of drop at 400 = ? m.o.a.

If you have 20" of bullet drop at 400 yards they you divide 4" into 20 to find out how many MOA up you dial the scope. As at 400 yards a 1 MOA angle will intersect the arc of a circle in two places and the arc length with be about 4" for all practical purposes. So 1 MOA is equal to 4" at 400 yards. To come up 20" from your zero on the scope you would turn the scope 5 MOA on the dial. Now most scopes move the POI about 1/4 MOA at 100 yards. But you are at 400 yards. So you are moving the POI 4 times what you would at 100 yards. So each click is 1 MOA instead of 1/4 MOA at 400 yards. So up 5 clicks should get your bullet on target at 400 yard if you are zeroed in at 100 yards and your scope is a 1/4 MOA per click at 100 yards. Does that make sense to you? If not watch the video that I posted the link to. It's by Ryan Clickner who is a Sniper Instructor and a US Army Sniper and works for the NSSF.
 
Originally Posted By: Don FischerWhat advantage it there to converting inch's to MOA? Seem's like a lot of figureing just to move 20". I've heard others say this is better too, just never could figure it out.

We convert the 20" bullet drop to MOA angle because the scope dials are calibrated in MOA's.
 
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