I am hoping one of y'all can give me a nearly sure-fire number to dial.

These are the bullets...

https://www.nosler.com/308-win...rade-ammunition.html

Being fired from a 16" AR10 with a silencer attached. ~850' elevation.

Confirmed drops out to 500m, off a 100m zero...

300m - 5.5 MOA
350 - 7
400 - 9
450 - 12
500m - 14.5 MOA

What should I dial at 600m? And, if it's easy-enough to figure, what's my drop at 550 as well?

Am I missing any relevant info?

This message has been edited. Last edited by: KSGM,

When I plugged what data available in my AB app it comes out to 17.43 MOA.
Couldn't figure out to insert your environmental data, so it's based now on Texas.

One other thing it shows 12.64 for 500 and you indicated something different.

Maybe download the app and plug in your own data to compare.

I just noticed that my data is yards not meters, so I might need to recalculate if that is the case.

Not knowing temperature and humidity.

I get 15.2 MOA foe 550 yards and 17 MOA for 600 yards.

ARman

New calcs for meters 100m zero

500m- 14.73
550m- 17.44
600m- 20.37

Assumption of velocity was 2525 based on Nosler published data.

Still Texas environmentals.

According to Copilot AI the drop in velocity from the 24 inch test barrel cited by Nosler for the load which was 2750 fps to 16 inches would be about 180 fps, or 2570 fps. Using sight height of 2.5" plus a temperature of 59 degrees and the standard pressure for that elevation (variations in humidity have virtually no effect), the Applied Ballistics data I got using a 100 meter zero were close to yours for 300 to 500 meters.

At 600 meters the drop was 19.85 MOA. At 550m the drop was about 17 MOA.

The difference between what I and smschulz got would be due to the different velocities we used.

Get yourself a good chronograph. Knowing actual velocity is critical for long distance ballistics calculations.
The correct sight over bore height also affects calculations a little.

This message has been edited. Last edited by: sigfreund,

This will be more than enough to set me up for success. Thank you, men.

Weather permitting, I'll be able to confirm these numbers on Wednesday. What you gave me will get me on target, and I can go form there.

I'll share my results. Hopefully I'll come away from the session with a good 10-shot group.

Bottom line -- 17 to 17.5 MOA elevation at 550, and 20 to 20.5 MOA elevation at 600 should be close enough to start.

On to the calculation details. Ballistics calculators are only as good as the data input. Sight height over bore is important. Accurate MV is really important. Accurate flight characteristics of the bullet is really important. Atmospheric conditions become increasing more important as distances increase beyond 400-ish yards.
- I used 2.5 inches sights over bore, which I find in the ballpark for most ARs.
- I futzed with MV. Sigfreund's estimates in the mid 2500s are likely pretty close.
- Accurate atmospheric conditions generally require elevation ASL, station pressure, temp, humidity. I like going straight to air Density Altitude. I used 2500 feet, but it could be between 2000 and 3000 feet. I use a Kestrel for my own DA, which has worked in ballistic tables for Texas in the winter (DA of -1000 feet one morning) through New Mexico mountains in the summer (DA of a touch over 10,000 feet some afternoons).
- I used Litz's data for the Nosler bullet. It should be pretty good, although I'm not fond of Nosler bullets. I find their accuracy, BC, and transonic stability to be less than Sierra and Hornady bullets.

On to dope. Listed actual results make it a bit challenging to back into accurate ballistics data.
- The drop from 300-350 increases by 1.5 MOA.
- The drop from 350-400 increases by 2.0 MOA.
- The drop from 400-450 increases by 3.0 MOA.
- The drop from 450-500 increases by 2.5 MOA.

Anyone who regularly shoots multiple long distances knows there is some data inconsistency here. Bullet drop increments generally increase on a somewhat linear pattern as target distances increase. At least above transonic bullet velocities.
- I would expect (and ballistics programs agree) that the 400-450 drop increase should be more like 2.5 and the 450-500 drop increase should be more like 3.0 MOA.
- This implies the the 500-550 drop increase should be at least 3.0 MOA, and the 550-600 drop increase should be at least 3.5 MOA.
- Part of the issue might be that the OP's measuring system (i.e. scope elevation turrets and reticle subtentions) are likely .5 MOA at the minimum. If so, ballistics calculations much smaller than .5 MOA -- as in hundredths of an MOA -- are moot. In shooting practice, POA and turret/reticle holds really can't be finer than 1/2 of the optics systems adjustment capabilities.
- For example with my own tables for competition & training.... I have MOA optics with 1/4 MOA turrets. Ballistics program data of 5.36 MOA rounds down to 5-1/4 MOA, which I list as 5.2 on my scope or wrist data cards. I know I can't dial 5.2 MOA on a turret that dials only 5.0 or 5.25 of 5.50, but the second decimal numbers is moot, and just adds an unnecessary digit to a dope card. I shoot in field conditions, not with a rail gun from a bench. And anyone who can consistently shoot with 1/4 MOA accuracy at distance in field conditions is a better man the I.
- Part of the dope issue might be that there is some variability in the POI data -- i.e. the groups are showing some vertical variation that is greater than ammo/rifle/sights capabilities.

My gut tells me that the dope's drop increases would be better measured in 1/4 MOA increments to predict flight beyond 500. But again, assuming that the target size is somewhat generous, the predicted elevations of 17-ish and 20-ish are good places to start.

Well, unsurprisingly, this was a humbling experience.

Installed a generous (about two feet wide) gong at 600m. Dialed 20MOA of elevation. Ding! Thanks SIGforum! Ding. Ding.

Travelled to the target and observed all three hits on the right edge. Two right next to each other at center height, and one lower.

Feeling pretty good, but wondering about the windage. Compensating for wind is something I have no proper experience with. I opted to dial 1MOA of left windage for the following shots. So far, there had been little-to-no perceptible wind.

I installed a cardboard target in front of the gong, with two ~1MOA squares on it. One for the first shot, and the other for nine more.

Returned to the shooting position. The first shot was not expected to hit the gong behind the target; it didn't. The trouble came when the others didn't either. I opted to stop shooting after five shots, but it turned out I had actually shot six. The lack of gong impact had me concerned about wasting ammo. A breeze had developed. I did see one dust kick-up to the right of the target.

Upon travelling to the target, I found that zero shots had impacted my generous cardboard backer. Based on evidence of impact in the dirt, I determined that the wind was now pushing them about 6MOA to the right.

I am learning, and I am determined to have something on that darn target.

I opted to dial 6MOA more windage, and re-engage one more time with my four remaining rounds in the mag. I wasn't eager to break into the next box of ammo, considering my lack of prowess in the wind.

I aimed at the right-hand square (the one that should ring the gong) and had no gong hits. The target revealed the four shots hit the left target. So, after dialing 7MOA of windage, I ended up with four rounds with a spread of 12", about 19 inches from my POA.

I am happy to have confirmed the 20MOA data. I am also happy to have had a real experience with wind. All feedback is welcome.

Stretching your boundaries is a good learning experience. At distance, wind call skills are a significant part of marksmanship skills.

You should use a ballistics program. JBM ballistics is free on the web. "Trajectory (Simplified)" is a good place to start. How I'm looking at data:
- Library -- This is bullet selection. Drop down to Nosler 308, 168gr, Custom Comp (Litz)
- Muzzle Velocity -- I used 2530 fps
- Sight Height -- I used 2.5"
- Wind speed -- 10 mph
- Minimum range -- 0
- Maximum range -- 700 (but 600 is fine)
- Range increment -- 10 (but 50 is fine)
- Zero range -- 100
- Altitude -- I used 2500 ft, with the box below "Pressure is corrected" being checked. This uses Density Altitude, and thus eliminates the need for true pressure & temperature numbers. But it requires a DA calculation, which I get on-sight from a Kestrel wind meter.
- Click the box on the bottom left "Ranges in Meters"
- Let everything else go the standard options that come up when JBM is opened.

Now I don't measure target distances in meters. Never had a reason to. No competition or training facility I've been to in the USA uses meters. Even the schools that cater to military, contractors, and agencies use yards. All my dope cards are in yards. If you ever find yourself having to range an unknown distance with an MOA reticle, you'll understand why MOA optics users say ixnay really quickly to meters.

The above data input results in 600 meter drop of 20 MOA, which is the 3rd column of the data output. Wind drift for a 10mph crosswind is 6.3 MOA. This means wind directly from the right or left at 10mph. Winds from anything other than 3 o'clock or 9 o'clock have lesser drift effects, but that's a whole 'nuther story. Wind drift in MOA is a linear function to wind speed in MOA. Thus, a 10mph wind drift of 6 MOA translates to a 5mph crosswind drift of 3 MOA, and a 20mph crosswind drift of 12 MOA.

Wind speeds vary, sometimes significantly, sometimes very quickly. Your bullet flight time is predicted at 1.025 seconds, during which a lot can occur. Wind won't be the same at the shooter, at mid-flight distances, or at the target. Early-flight wind affects drift more than late-flight wind. Wind speeds are higher at greater distances above the ground, but that's also a later topic.

Learning to judge wind speeds takes time and repetition. It's almost impossible to do without a wind meter of some type. Wind flags help, but only a few types of competitions allow those.

I don't know what type of reticle your scope has, but if it doesn't have MOA subtentions on the horizontal crosshair, it's value for shooting at distance in wind is minimal. As in really, really minimal. There are very few times when dialing wind is reasonable:
- Shooting a horizontally moving target, that is on a track, and goes back and forth. Assuming the wind is reasonably constant, one dials the best guess of wind, then the target leads are the same in both directions. I've done this a few times.
- Shooting at very long distances with high crosswinds. I've done this quite a few times in ELR comps in Wyoming. The 1000-1600 yard targets required 20-25 MOA of drift holds. So that I could place the targets more in the center of my optics, I sometimes dialed 10-15 MOA of wind, then held the rest via the reticle.

Shooting carboard at distance doesn't work for immediate feedback, which is mandatory for wind drift corrections. The steel gong is your friend, and it should be freshly painted white or yellow. Or maybe light orange. That way you can see the impacts on steel. Misses can be spotted easily in dry dirt. Once the impact has been noted, one corrects windage as soon as possible, before the wind changes significantly again.

Based on my dialed windage and the end result, I was contending with a (variable) 4MOA push to the right.

I know my intermingling of MOA and metric measurements is stupid. My scope happens to be in MOA, and I am used to using MOA as a standard of accuracy and unit of measurement when considering dispersion, drop and adjustments.

However, my time in the military has my head in metric, when it comes to measuring distance. That's how the maps are, and how we considered things when travelling or estimating range.

I wasn't a long distance shooter in the military, so I never did consider any of this stuff the way I am now.

Also a noob in shooting any real distance, so a noob question.
Fritz: “Early-flight wind affects drift more than late-flight wind.”

I was told the exact opposite. At the target where the bullet is slowing would be hit with more effect.
Now this is just from toobyou vids and not experienced shooters.
***
I have an el-cheapo Caldwell windmeter but it seems to work. It is just wind and temperature, not a weather station. All other environmentals have to come from other sources.
OnXHunt for altitude cross checked with a downloaded barometer program.
(OnX will also tell me if I’m on Nat. forest or State Trust land, a big deal in AZ)

4DOF from Hornady is what I’m using for ballistic calculations, plus the price is right. Free!
Just being able to swing the wind chart to the prevailing direction, dial the speed and target yardage makes that pretty easy.
As noted before, it requires an accurate muzzle velocity. Box labels are suspect.
The measurement of optic above bore can set to tenths of an inch.

quote:

Early-flight wind affects drift more than late-flight wind.

This question has been debated for literally as long as I can remember going back decades. It wasn’t too long ago, though, that I read a statement by ballistician Bryan Litz that confirmed what fritz says. I believe most of the earlier debate was among people who were just guessing based on what “ought” to be.

But if someone believes he can settle the question himself, I’d say do it and let the rest of us know the results. As Admiral Hopper observed, one accurate measurement is worth a thousand expert opinions. The problem is of course that it would be very difficult for most people to be able to make an accurate determination. Litz and crew, though, do have very sophisticated instrumentation that may make it easier for them and I’d certainly trust his opinion before any guesser’s.

And ultimately what matters is what the bullets tell us: i.e., where do they end up when shooting in the wind?

I started a separate discussion of near versus far winds here: https://sigforum.com/eve/forum...880086515#4880086515

Bullets can't self-correct or self-change flight vectors in mid-flight. Once a bullet is deflected laterally by a wind force, it stays deflected on that path, until another wind force acts again. Let's say there's a one-time small-window distance that a wind gust from the left occurs, for a 600 yard target. Either at 100 yards and at 500 yards.

Let's say that the wind gust at 100 yards produces a flight deflection of 1 MOA. The bullet will remain flying on this vector all the way to the target, assuming no wind for the remainder of the flight. So...it lands roughly 5 inches right of POA. 500 yards at a 1 MOA changed vector.

The same wind gust from the left at 500 yards will have more effect on the now slower bullet than it will at 100 yards. Depending a bunch of factors, it might be 20%, maybe 40%, maybe even as much as 60% more. So...it lands maybe 1.2 to 1.6 inches right of POA. Not even in the same league as the gust at 100 yards.

Now nobody -- and I mean nobody -- in steel/precision/PRS competition tries to estimate the additional percentage drift change on late-wind. Too hard to calculate, no time for it. Experience gives one a ballpark feel, and you give it your best guess. One just knows that early-flight wind is a bigger drift problem than late-flight wind.

Anyone who has trained or competed in variable terrain, with variable winds, shooting in various directions, at various distances understands this. If you don't, you get your ass kicked really fast by those who do. The folks who think wind at the target matters more are likely bench shooters, at public ranges, with trees or large berms on both sides of the shooting lane, and with relatively consistent wind directions. And these folks likely shoot 3 round groups at 100 yards. And they can shoot "sub-MOA all day long", maybe "if they do their part".

Nobody who has shot Steel Safari in New Mexico, Competition Dynamic's Team Challenge in Wyoming, or ELR matches in Wyoming will state late wind affects bullet flight more. Or the Coal Canyon precision matches at NRA Whittington center. Or field matches in Nebraska, Kansas, Utah, Montana, or Oklahoma.

quote:

Now nobody -- and I mean nobody -- in steel/precision/PRS competition tries to estimate the additional percentage drift change on late-wind. Too hard to calculate, no time for it. Experience gives one a ballpark feel, and you give it your best guess. One just knows that early-flight wind is a bigger drift problem than late-flight wind.

I DID state this was a noob question.
After looking at Brian Lizt vids he stated that, yes, the wind at the shooters position is usually the most dominant.
The effect from late wind in flight “could be from shooters that have a protected firing lanes where the bullet isn’t affected by early wind. In those cases the wind downrange could be more influential.”

Litz vid

quote:

Originally posted by KMitch200:
The effect from late wind in flight “could be from shooters that have a protected firing lanes where the bullet isn’t affected by early wind. In those cases the wind downrange could be more influential.”

Yep. This is part of increasing one's skills reading wind.

Litz is one of the best shooters out there, having both great shooting skills and great technical bullet flight skills. But he's not infallible. I've shot in the squad after him at an ELR competition near Casper, WY. The range is in rolling hills, right next to a major wind generation farm. I saw Litz struggle on a few stages, shaking his head on how wind was tough to call. This was not a confidence builder for any of us, as we waited for our turn to shoot.

The hardest wind conditions that I've ever shot in was a Battle of Breakneck PRS field match, held about an hour's drive north of Sidney, NE. Probably close to 10 years ago now. A number of shooters measured wind at 40+ mph on the canyon ridges from where we shot. Midday brought driving rain, mixed with intermittent snow by late afternoon. The narrow & wide canyons we shot through & across produced regions of calm winds, swirling winds, accelerating winds, up drafts, down drafts, and everything in between. For the 200-ish shooters at that match, I doubt anyone will ever experience a rougher day of shooting. I'm certain there are youtube videos about that day. Pretty certain we Colorado shooters at that match discussed it in the SF long-distance rifle thread.

*****
Wind gradient is the term generally used for higher wind speeds of wind layers, as elevation above ground increases. For targets out to a few hundred yards on smooth & flat terrain, it's not an issue. But for long distance targets, the bullet's flight curve often breaks into a layer of higher wind speeds.
- The peak height of a modern bullet's flight generally occurs about 55-60% of the distance to the target. Some folks call this "max ord".
- For my 6.5CM at 3000' DA, max ord for a 1000 yard shot is around 12 feet. My instructors at Rifles Only state this is the around the point where wind gradient comes into effect. The wind speed often increases for roughly every 10 feet of elevation, possibly in the 5-10mph ballpark.
- For my 6.5CM at 3000' DA, max ord for a 1400 yard shot is around 21 feet. This may result in the bullet travelling through 2 different wind speed layers --- more time in the lower of the 2 layers, but just briefly in the higher layer.
- This is one the challenges with ELR shooting, especially with a non-magnum caliber such as 6.5CM.

I still remember an old cartoon whose character says, “Anyone who believes there’s no such thing as a stupid question has never listened to a political news conference.”

When it comes to something like firearms ballistics, how do we learn? Research, including questions. And because so many shooters have had so many mistaken ideas for so long, it’s inevitable that sooner or later we’ll run into conflicting claims. As part of the instruction I give, I have students complete short surveys that include questions about ballistics. I’ve had even former military snipers and designated marksmen get answers wrong because of something they were told by someone who was equally ignorant, and they never questioned it further.

I’m most impressed when someone does push back to something I tell them because it demonstrates that they’re paying attention and that they paid attention to something they learned before. Even experienced long range shooters are often not interested in delving deep into the technical aspects of ballistics, but anyone who reads Bryan Litz’s books and watches his videos as well as consulting other research materials available can become a 1 percenter in knowledge about the subject.

Gents,

For years I have used 15 MOA as my elevation for 600 yards. Rifle is a GA. Precision "Rock" chambered in .308/7.62 x 51mm with a 23-inch barrel. The load is a 175 Gr. SMK at 2650 FPS.

Proven rifle and proven load. The 15 MOA elevation has held standard for most of my other rifles, too. Plus or minus .5 MOA.

Wes