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| Freethinker |
Ah, always good to learn something new. But now having to count by base eight rather than four doesn't make it any easier.  Anyone calibrate their reticles and adjustments in gradians? ► 6.4/93.6 | |||
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| Member |
-I am thinking about mounting this on a 20" Ar15 flat top upper receiver. -As far as ammo nothing match just what I have laying around 55 and 62 grain. -Targets would be standard silhouette targets, man sized targets. The distance I would like to reach is maybe to 600 yards/meters maybe more, as far as I could get out to using the specified rifle and ammo combination. -I am not shooting match ammo so just hits on a standard silhouette at the different ranges that my set up is capable of. Once again thanks for everyone that has contributed to this thread thus far. | |||
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| Member |
Always Mr. Funnyman, are we? Folks who use a 1/8MOA knobs in F-class will do absolutely no conversions. Here's the way I do it. Let's say I'm going from the 600 yard line to the 1000 yard line. My little Blue Book (yes, named after the 1960 USAF project) has the number of MOAs for come-ups. Let's say it's 20.5MOA. What I will do is look at the number and tick on the know and count 2 revs up from there (my scope has 10MOA per rev) and then add 4 clicks (.5MOA). Easy peasy. Now as I approach the line to get ready to shoot, I have been looking at the flags and I decide that they look like about 2MOA from the right. I don't know how fast the wind is in FPS or MPH, I just know the flags look like a 2MOA correction. I dial that in from my mythical "1000 yard zero", and go to town. As the barrel heats up or front or rear wind changes, I will probably add a click or two of elevation during a string of 20 rounds. I am holding on paper for windage, but I have been known to dial windage in extreme conditions, like when I have to hold off my target and on to the next one or more. At the Nationals, State and Worlds, they don't stop for nothing except lightning or absolute torrential downpours. (They would ruin the targets. Nobody cares about the shooters, that's why we pack rain gear and have rain shields for the ammo and action.) When Im done for the day, I write down my settings in my Project Blue Book with some notes about conditions and reset windage to "0". I record the elevation, just in case I forget where I left off the next time. (It has happened.) | |||
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| Freethinker |
Thanks. All of that is pretty much common sense as you describe it for that type of shooting, it seems to me, but it’s good to have it explained clearly. Your comment about scopesights with 1/8 MOA adjustments piqued my interest, and sure enough, there are many more offerings than I expected. I will say, though, that if not “rare” as I originally opined, I would revise it to uncommon—at least as compared to all the other alternatives. If a sight like that is particularly well suited to a specific sport we would obviously expect to see more of them at such events. I would expect that fewer scopes with 1/8 MOA adjustments are used in competitions when significant sight adjustments are required under tight time constraints like the events shown in all the National Rifle League videos I’ve been watching. ► 6.4/93.6 | |||
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| Sigless in Indiana  |
Spending a few bucks on Strelok Pro is absolutely 100% worth the money. Pull the data for the cartridge you want to shoot. (Real data, not manufacturers listed data on the box, which is from a 24" pressure barrel). And plug it into any of the reticles that are in the scopes you are considering. Throw in some wind and see if you want wind holds as well. For 100-600 yards with factory 55 and 62gr ammo. You could do a lot worse than a Vortex PST Gen2 3-15 FFP with either the MRAD or the MOA EBR-2C (or D?) reticle. Generate a dope card, set your zero stop, and you can hold for wind and elevation, OR dial for both, OR some combination thereof, and be making hits on torso sized targets with ease. There is actually a function in strelok pro where you can dial a simulated turret on your phone, while looking at a reticle display, and the app will adjust your hold on the reticle display. Really slick. | |||
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| SIG-Sauer Anthropologist |
That´s correct, but not the whole story. The purpose of the dots is for estiating shooting distances. With the dots with or hight of an estimated size is measured and shooting distance is calculated based on this estimat. Then the reticle is adjusted based on the information of the ballistic curve for the distance you want to shoot. If you do all of it in metric, there is no problem. If it´s done in feet and yards you might run into a conversion problem with mil dot. If you shoot at known distances only or if you have a spotter, it does not matter. The bottom line is how fit one is with trigonometry and conversions. Here is a real world question. Your scope is zeroed at 200yds. An item with the size of 4" measures 2 mil dot. How many clicks do you have to adjust and in what direction? | |||
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| Member |
OP -- Let’s start with ballistics assumptions, to confirm the scope’s holdover reticle. I’m guessing you’ll see about 3050 fps muzzle velocity from many 55 grain FMJ loads. You’ll probably have a 2.5” sight-over-bore height, and I’m guessing air Density Altitude of 3,000 feet, and zero at 100 yards. Using JBM ballistics for a generic 55 FMJ bullet, elevation requirements in mils for the distances: 1.0 mil – 300 yards 1.9 mil – 400 yards 3.0 mil – 500 yards 4.4 mil – 600 yards The holdovers line up really well with the reticle for 300, 400, and 500 yards. The reticle indicates about 4 mils for 600 yards, versus my guess of 4.4 mils. The horizontal ranging bars for an 18” wide target are probably reasonable. Standard IPSC targets are 18” wide – and 24” tall through the body. The holdover reticle has markings through 15 mils, which in theory is for targets at a little over 1,000 yards. To be honest, at such distance your target may need to be a conex container with 55 FMJ ammo for a reliable hit. This scope allows for both dialing elevation and holding elevation via the reticle. I’m guessing you want it for the holdover capabilities. Understand that a holdover reticle is based on an estimated formula for a given muzzle velocity, bullet, and air density. The reticle may be close for your use, but it almost certainly won’t be exact. ***** Moving on to accuracy. 55 FMJ loads are rarely more accurate than 2 MOA (.6 mils) at 100 yards. Could be closer to 3 MOA (.9 mils) accuracy, and it will only get worse as distances increase. At 600 yards an IPSC is 3 MOA (.9 mils) wide and 4 MOA (1.2 mils) high. If your ammo is capable of only 3 MOA (.9 mils) accuracy, this is your realistic limit of getting a high-percentage hit. Not a well-placed hit on an IPSC-sized target, but an impact somewhere on the target. Next up is crosswind effects on the 55 FMJ bullet. A 10 mph crosswind (from either 3 o’clock or 9 o’clock) pushes the bullet sideways 8.5 MOA (2.5 mils) at 600 yards. Assuming you shoot at locations with winds, you could have wind holds that are much larger than the width of the IPSC plate. Coupled with marginal accuracy of 55 FMJ ammo, realistic hit rates on an IPSC at 600 yards could be really low. Bottom line – if you want reasonably consistent hits at 600 yards, you should change ammo. And possible look for an optic with higher magnification. If you’re willing to shoot at closer targets and accept hits throughout the IPSC-sized plate, you’ll be fine. IMO the 1-8x scope you list – coupled with the rest of your rifle system -- could serve you fairly well for targets out to 300 yards, maybe 400 yards. | |||
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| Member |
On to how the windage portion of the reticle works. Using my ballistics assumptions above, the wind drifts for a 10mph crosswind are: 1.0 mil at 300 yards 1.4 mils at 400 yards 1.9 mils at 500 yards 2.5 mils at 600 yards The windage dots are on 1 mil increments. If you're shooting at 500 yards, the drift for an effective 10mph wind is 1.9 mils, which is about 2 dots to the right or left of the reticle's center. If the effect crosswind is 5mph, the wind holds are 1 dot to the right of left. Wind drift formulas are linear. So...at 500 yards a 20mph wind results in 3.8 mils drift. A 13mph wind results in approximately 2.5 mils drift. Wind that is from a different direction than 9 or 3 o'clock also drifts the bullet, but with less effect than from 9 or 3. That's a whole different topic, but this is at least a start. | |||
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| Member |
Next -- inches, centimetres, yards, meters, fathoms, and metric vs. imperial kumquats.... Both MOA and mils are forms of angular measurement, just done on different scales. The greatest part of a First Focal Plane optic is the angular accuracy of its reticle at any magnification and at any distance. As distances to targets increase, as the quantity of targets at various distances increase, and as the time to engage targets decreases -- the desire to deal with linear measurement at targets decreases. Back to the OP's 55 grain potential ballistics at 600 yards. - Elevation dope is 95 inches, 242 cm, 15.2 MOA, or most appropriately for his scope 4.4 mils. He can either dial or hold the elevation. - Windage dope for a 10mph crosswind is 54 inches, 136 cm, 8.5 MOA, or more appropriately for his scope, 2.5 mils. He can either dial or hold, but holding makes more sense. We can easily view and determine angular values in our FFP scopes, but linear measurement at the target must be calculated. Well, unless there's a flashing neon sign above the target which states "look at me, I'm a 15" circle". I haven't seen such signs on targets, but my experience might be lacking.... When we miss a target and have the opportunity for a follow-up shot, we can measure the miss with our reticle. Then adjust the hold/turret to send the next shot on target. No conversion to linear measurement, just angular correction. Doesn't matter if the scope is mils or MOA -- either works. **** One challenge with mils vs. MOA scopes comes in competitions, where members of teams or squads may provide windage feedback to other shooters. Shooter #1 might say "I needed 2.3 mils of wind from the right on the last target". Which is great if everyone is using a rifle/bullet/MV with similar ballistics. But if shooter #1 is using a fast 6 Creedmoor with a high-BC bullet, his windage dope will be much less than what shooter #2 needs with a pokey 168 grain 308 Win. However, if shooter #1 says "I needed 11 mph of wind dope for the last target", shooter #2 goes to his dope card and knows exactly what to hold for wind. Now shooter #2's hold may be almost twice as much #1's hold, but the knowledge of effective wind speed works for both shooters, with dramatically different rifles. | |||
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Member |
********************************************* Waiting to hear the answer from someone. As I can only quess. | |||
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The guy behind the guy |
Funny isn’t it. I never use the markings. I always count. | |||
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| Member |
It's not a real-world scenario for me, but I'll play. I have MOA scopes, but I know that a 4" target measuring a little under 7 MOA (a quick and dirty conversion from 2 mils to MOA) is really, really close. I don't zero any of my rifles at 200 yards, but I know the rough trajectories at close distances for a 200 yard zero. A 4" target up close -- say 50-ish yards -- means I'd aim center of target, knowing that the trajectory will be within an inch of target center. I wouldn't take the time to do any calculations, I wouldn't change elevation via clicks, I wouldn't change elevation via reticle holds -- I'd just take the shot. So....I ran the calculation with the mil ranging formulas. The target is about 55 yards away. With my 6.5 Creedmoor under these conditions, JBM says the predicted POI is .4" higher than POA. Bingo, I just about center punched the target. | |||
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| Member |
My quess would have been, the target is twice as big so 100 yards and clicks down 5. But in my mind I'd just shoot a little low. I have no experience with reticles. . | |||
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| SIG-Sauer Anthropologist |
It was not really the intent to have somebody to calculate the adjustement. But thanks. Mit MOA it´s not really challaging. He quesition was more of a hint to show the conversion problems one can run into when metric MIL DOT was used for ditances measured in inches and yards. My conclusion is: When one is planing to shoot on American ranges, beeing used to inches, feet and yards one is better served with a MOA reticle in a scope having 1/4MOA or 1/8MOA adjustment turrets. | |||
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Plowing straight ahead come what may |
What ever the reticle...hold between the nutsack/groin and the throat/head and you will make “the shot” within reason...not to be confused with precision paper shooting For gropes need not apply (this sounds like good instruction to my pea brain) ******************************************************** "we've gotta roll with the punches, learn to play all of our hunches Making the best of what ever comes our way Forget that blind ambition and learn to trust your intuition Plowing straight ahead come what may And theres a cowboy in the jungle" Jimmy Buffet | |||
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| Freethinker |
Yes, counting is my primary method too. If I am in shooting position I can’t focus well enough on the markings to be sure of the adjustment, and when I can see them I usually just rely on the markings for confirmation of my count. ► 6.4/93.6 | |||
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| Member |
I doubt you have much personal experience with reticle ranging. If you did, you wouldn't have used an example of a "4 inch target measuring 2 mils". Nobody would range such a target, as with our bare eyes we would know it's very close. A 4 inch target measuring .2 mils or .4 mils would have been a more reasonable scenario. Furthermore, a 200 yard zero would not be used by a precision shooter -- it more likely would be on a hunting or self-defense rifle. The shooter wouldn't measure such a target with their reticle. Like my answer above, they're know the target was roughly near their first zero. They'd hold dead on like I did, and they'd smack the target. Like a hunter trying to center punch the heart of a deer at 55 yards. I will only speak for USA's precision/steel/PRS/NRL type matches. The majority of these shooters use mil-based scopes. The vast majority of best competitors use mil scopes, with hardly any top shooters using MOA scopes. Here's an real world example of what goes on in such competitions. Me, with a 6.5 Creedmoor and MOA scope. The target is a 617 yards. Maybe I ranged it, or maybe the distance was given to me. It doesn't matter. No target size was given, and I didn't try to calculate the target size via my reticle. My dope table shows I need 11.8 MOA of elevation and 2.6 MOA of wind for a full-value (i.e. 10mph crosswind) for a target at 620 yards. My tables are built in 10 yard increments. I guesss that we have a half-value (5mph) wind from the right, which means my wind hold is 1.3 MOA. In my reticle I see the target is about 2.5 MOA wide -- about the wind drift of a 10 mph wind. So...I dial 10.75 MOA of elevation and place my crosshairs on the right edge of the plate -- if I think the wind might gust to higher speeds, or just inside the right edge of the plate if I think the wind might die down a bit. My buddy, with a 6.5 Creedmoor, mil scope, and a Kestrel to calculate dope. He enters 617 yards, and gets a solution of 3.4 mils of elevation and .8 mils of wind (for 10mph crosswind). The actual wind hasn't changed for him -- it's still about 5mph from the right. He gets on scope and sees the target is maybe .7 mils wide, or a touch less than the full-value wind hold of .8 mils. Like me, he holds either right edge or just inside the right edge and breaks the shot. Mils or MOA -- it makes little difference. | |||
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| SIG-Sauer Anthropologist |
I´m using a Hensold 4x24 on a SIG 550. It´s DMR zeroed according the recommendations of Swiss DOD. If it does no fit your idea, you might argue with them. It does the same trick in field shooting events like you are used in your precision shooting events. My rifle precison shooting experience is limited to 300m Standard rilfe only. I learned reticle ranging back in the 80´ with scissor scopes as forward obervator with the infrantry. Instead of "dope charts" we used trajectory maps related to the charges of the grenades. You might explain to me the diffrence between this and a rilfe. The method is always the same and not a matter of experiance but math skills. Holidng off center to compensate what the reticle can´t do is related to experience. However the OP wanted to know the difference between MOA and MIL DOT. Regarless of who is using what in which situation, it´s the math involved to get a realistic range estimate. MIL = 1/1000 rad. MOA = 1/60 DEG. | |||
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| Member |
4” target at 56 yards, if my rifle has a 200 yard zero, I think I would just put the cross hairs on the middle of the plate and give her a tug. Ranging with a reticle is stupid and I only do it if it is required by a stage at a match. I have multiple tools to determine the exact range, or I would guess before I would reticle range. If you want to. Knock yourself out Known size of target in inches x 28 (I round) divided by measurement of target in mils equals distance in yards. People on the internet say they can measure the target to the nearest 10th of a mil, and come up with the real range every time, I suck at it, and I have seen first hand how bad everyone else sucks at it too, so I have a Terapin, and a couple of back ups that all do way better, and are certainly faster. I shoot mostly at steel targets from field conditions, they don’t shoot back, and never run away. | |||
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| SIG-Sauer Anthropologist |
Shooting experience and what you are thinking about mine or my example is irrelevant for this discussion. The difference between indexed MOA and MIL RAD reticles is a math. When you measure in inches and want to convert to yards you need to convert it with the factor 36. For people being challanged with math or have not got a calculator handy, the factor 36 is not easy to compile. This is the reason why MIL RAD is better suited in the metric system. MOA on the other hand is better suited for «American» distances for the same reason and a challange when it´s used on metric distances. Either way you will end up with odd numbers that don´t mean a lot if one does not know how the math behind the two systems work and what it means when you do the adjustments. | |||
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