Any thing for a moa/moa scope? The mil wind estimation is great. All I have is moa. If there is a trick for moa, can you explain it in depth and give a couple of examples with math if there is any. Please and thank you.
Deano
Deano
(Distance in yds X wind in mph)/constantAny thing for a moa/moa scope? The mil wind estimation is great. All I have is moa. If there is a trick for moa, can you explain it in depth and give a couple of examples with math if there is any. Please and thank you.
Deano
A mil is 3.438 moa. So, a mil wind is a 3.438 moa wind right? So, you can use the first number of your G1 BC and know that, that is very close to a 3 moa wind for you using moa. Therefore, multiply the yard line by 0.3.Any thing for a moa/moa scope? The mil wind estimation is great. All I have is moa. If there is a trick for moa, can you explain it in depth and give a couple of examples with math if there is any. Please and thank you.
Deano
With something like a Creed, a 10mph wind moves the bullet 6moa instead of 10moa at 1000 yards, so that is why I do it the way mentioned above. The traditional, historical British method's fatal flaw is that it assumes a 10mph wind = 10moa at 1000 yards. Very few people are launching those types of bullets these days.The British method works for MOA scopes
The Long Hand formula in that video is bad, the constant is wrong that is the constant for a 168 / 308 only you have to fix it for higher BC bullets
If you are doing long hand math in the field or on the firing line you already lost, we stopped teaching that stuff a while ago
British formula
10MPH wind is your base wind. (wind speed that equals 1moa per 100 yd)
Off of base wind 2-3 = light 5 = medium 10 = base 20 = heavy
Example
Range 600, velocity 10mph = 6 moa
Range 600, velocity 5 mph = 3 moa
Range 600, velocity 2-3mph=1.5 moa
Range 600, velocity 20 mph = 12 moa (and call for indirect fire)
Interesting topic but my head is spinning a bit with all the back and forth. The BC method sounds very useful although I am an bit confused on how to figure it out for my specific rifle. I have a Rem 700 with 16.5 barrel with a 1/10 twist and use Fed GMM 175s that ave about 2400FPS. The box says my G1 BC is 0.496 and G7 0.243. Not sure where to go from from here.
The BC for the standard .308 is .4xx so you use a 4 mph window.
I don’t know what the “standard” is per se. 168/175 gr probably but most .308 bullets fall in that .4xx BC realm (flatlines excluded). The BC method is based off G1. So you said a .496 g1 for your 175; so that’s a.4xx or you could even use 5 but 4 is better.This may be a stupid question but what is considered the standard i.e. is it different than the BC I listed above. BTW G1 or G7?
Cheers
At an elevation of 2000ft your base wind/mil wind is going to be a 3.5mph wind due to how slow it is starting to begin with. But using 4mph will work just fine for you to 800 yards which is where you go subsonic anyway.Interesting topic but my head is spinning a bit with all the back and forth. The BC method sounds very useful although I am an bit confused on how to figure it out for my specific rifle. I have a Rem 700 with 16.5 barrel with a 1/10 twist and use Fed GMM 175s that ave about 2400FPS. The box says my G1 BC is 0.496 and G7 0.243. Not sure where to go from from here.
What you said is absolutely accurate, but it just doesn't have to be that complicated. Just know that the same bullet pushed 200fps faster than 2800fps gets another 1mph added to it's basic wind. If the bullet is 200fps slower than 2800fps it loses 1mph.The BC for the standard .308 is .4xx so you use a 4 mph window.
100 = .1 mil at 4 mph
200 = .2 mil
300 = .3 mil
400 = .4 mil
500 = .5 mil
600 = .7 mil due to velcity bleed off and correcting the estmate
700 = .8 mil
800 = .9 mil
900 = 1 mil
100 - 1.1 mil
Every four mph window then becomes a multiple so 16 mph wind at 500 is 4 times .5 mil or 2 mils.
This can be used for 5.56 with a BC of .3xx, using 3 mph windows, the 300 Win Mag with .5xx BC using 5 mph windows and so on. Adding .1 mil to the window for each mph, ie 5 mph at 500 is .6 mil will get you on the target.
Yes. I didn’t add any any correction for the lower velocity due to the shorter barrel.What you said is absolutely accurate, but it just doesn't have to be that complicated. Just know that the same bullet pushed 200fps faster than 2800fps gets another 1mph added to it's basic wind. If the bullet is 200fps slower than 2800fps it loses 1mph.
The BC for the standard .308 is .4xx so you use a 4 mph window.
100 = .1 mil at 4 mph
200 = .2 mil
300 = .3 mil
400 = .4 mil
500 = .5 mil
600 = .7 mil due to velcity bleed off and correcting the estmate
700 = .8 mil
800 = .9 mil
900 = 1 mil
100 - 1.1 mil
Every four mph window then becomes a multiple so 16 mph wind at 500 is 4 times .5 mil or 2 mils.
This can be used for 5.56 with a BC of .3xx, using 3 mph windows, the 300 Win Mag with .5xx BC using 5 mph windows and so on. Adding .1 mil to the window for each mph, ie 5 mph at 500 is .6 mil will get you on the target.
Well if at 500 and a 4mph wind gets you a .5 hold, then a 5 mph wind would be a .6 hold at 500.I'm tracking on what you said, as well as what Skookum added to it a few posts down, but your last sentence here has me confused. Can you explain that for the math challenged, like me?
Now I'm tracking again, thanks! Missed the idea that you were jumping from 4mph to 5 mph.Well if at 500 and a 4mph wind gets you a .5 hold, then a 5 mph wind would be a .6 hold at 500.
If I'm understanding you correctly, then no, you should stick with 4mph. The lesser wind will affect your bullet more, since it is slower than normal. If you went to a 5 mph wind, you would be assuming a greater BC than your bullet will give you at its lower velocity.SO with the lower velocity i.e. about -200 FPS since I think the box listed 2600 I would have to increase the mph due to the 175 only going about 2400. So maybe starting with a 5 mph window would be better?
I shot in some pretty tricky wind yesterday. I thought I would break it down here. I am shooting a 308 with 175 grain Nosler Custom Competitions. BC is pretty much the same as a 175 SMK so, G7 .243 & G1 .500ish. I am shooting an old gas gun load of 39.5g of IMR4895 @ 2484fps. Slow, but extremely accurate and consistent.
The bullet based on BC would be a "5", the initial assumption is that 5mph would move it 1 mil at 1000 yards.
I'm only shooting it just under 2500 fps, so we change that assumption down to at least a "4", this is our "base wind".
The range is 753 yards
The wind is 3-6mph from North, switching to NW.
We take the actual wind, and divide it by our base wind. We do it once for the low and once for the high, this is our wind bracket.
3 / 4 = .75, 6 / 4 = 1.5
Our standard full value hold for our base wind at 753 yards would be .753 mils, it's the range expressed as a decimal (753 / 1000)
.753 mils x .75 = .56 mils, This is our low side (3mph)
.753 mils x 1.5 = 1.12 mils, This our high side (6mph)
So our full value wind bracket at this range is .56 mils (.6) to 1.12 mils (1.1)
Now for the tricky part. The wind was swithching N to NW. So, it was coming right up my back then swithching a bit to my right.
I'm on the side of a mountain, shooting across a small canyon that opens up a bit to my left, creating a small bowl that I'm shooting across the mouth of. When the wind is 3mph, and coming up my back, there is no cross wind to deal with. Center hold.
When the wind kicks up to 6 mph, the wind following the mountain wants to fill in the bowl to my left creating a crosswind right to left.
This cross wind is right at 22-25 degrees, so half value. Let's do the math:
6mph = 1.1 mils x .5 (half value) = .55 mils (.6)
When the wind switches to my right, the wind comes at about 45 degrees, so .7 value.
3mph = .6 mils x .7 = .42 mils (.4)
6mph = 1.1 mils x .7 = .77 mils (.8)
So, this is the wind I was dealing with for about 3 hours yesterday. I wish I could say I hammered the target every time, but it didn't happen. The wind was extremely subtle, and the target I was shooting at was just larger than minute of angle. I shot 100 rounds in three hours, and I managed about a 40-50% hit rate, with most of the others being a tenth or two off the edge...a couple of handfuls I blew out of my ass and missed by a half mil or more. Shooter fatigue was definitely a factor toward the end.
So, hope this helps someone.
This is essentially the same math that I did above, but the way you handle the "left over" and add it to the rest is something I haven't seen before.So...I took a variation on the info put out by Mike/Frank and added a touch from a video I saw on YouTube and here's what I've come up with.
1. Start with the same 5mph, 90 degrees, and plug that in to your ballistic software.
2. You'll get whatever the wind data is. For my 6.5CM there were a lot of flat spots in the wind deflection, so in step 2, adjust the wind speed until you get a linear progression. Meaning: Increase wind until 100 = 0.1, 200 = 0.2, 300 = 0.3, and so on. For my 6.5CM shooting Prime ammo, it was at 7mph. It was "linear," until 1000, where it was 1.1. This makes it VERY easy to memorize.
3. So...after step 2, you have your base wind value. In my case it's a 7.
So...how do you "calculate," holds on the fly?
Ex # 1: 10mph full value wind at 600 yards
1. Take 10/7 = 1, with 3 left over.
2. 1 x wind dope at 600 = 0.6 = 0.6mil
3. Add the "left over," from Step 1. 3 = 0.3mil
4. So...total wind hold = 0.9 for a 10mph full value wind at 600 yards
Ex # 2: 5mph full value wind at 900 yards
1. 5/7 = 0.8, no left over
2. 0.8 x 0.9 = "72" = 0.72
3. No left over
4. Total wind = 0.7mil for a 5mph full value wind at 900 yards
Ex # 3: 20mph full value wind at 400 yards
1. 20/7 = 2, with 6 left over
2. 2 x 0.4 = 0.8
3. Left over = 6 = 0.6. 0.8 + 0.6 = 1.4
4. Total wind = 1.4mil for a 20mph full value wind at 400 yards
********************
This matches really well, it's easy to setup and memorize. My 6CM for example has a base wind of 8mph.
I haven't had a chance to take it to the range and see how it works out on steel, but it's lining up with the software and is easy to remember. Hope it helps.
This is essentially the same math that I did above, but the way you handle the "left over" and add it to the rest is something I haven't seen before.
I'm stealing that shit, just so you know.
I've been playing with this some more. I have been using ranges from 400 yards to 1000 yards and using base winds of 4 mph, 5mph and 7 mph to represent the 308 Win and 6.5 Creed class of cartridges.I just came on shift and didn't have time to read through the thread. Sorry for hijacking the method if it's similar. Like I said, it's a hybrid of a couple of different methods that I've found other than the base wind value, which sounds like what you do. I'm still really new to LR shooting, but am a bit of a math geek. So, hopefully this works out.
Appreciate the 'stealing that shit,' as I'll take it as a compliment.
What I have personally been doing is this...rounds that are traditionally stabilized at 30 - 32 calibers per turn, I use 2% of drop. For rounds that are stabilized at 28 calibers per turn or faster, I use 1% of drop. I'm still playing with it, but it seems to be working pretty well.I understand this method is a tool the shooter can use to get close in the field, and is not exact.
Is there any similar rule of thumb for accounting for spin drift? Or are you guys just adding a click or subtracting a click based on wind direction? Curious how (or if) you deal with it when shooting without referencing a ballistic app. Thanks.
What I have personally been doing is this...rounds that are traditionally stabilized at 30 - 32 calibers per turn, I use 2% of drop. For rounds that are stabilized at 28 calibers per turn or faster, I use 1% of drop. I'm still playing with it, but it seems to be working pretty well.
Lots of good ways to do it. If you are getting hits, then you are correct.In the spirit of answering the original question of "How do you dope the wind?", here is what I was doing before learning the BC method.
On my dope card that I would tape to the rifle, for each range next to the moa of drop, I would write the drift for 1mph of wind. Then in the field I would estimate the wind in mph, and multiply my 1mph wind drift by that estimate. So if drift at 400 yards at 1mph is 0.21 moa, and my actual wind is 4 mph, I would hold 0.84 moa into the wind (0.21 x 4 = 0.84). Simple.
Of course a ton of people do this, but most people I've talked to write the 5 or 10mph drifts on their dope card. To me, multiplying drift by the 4mph observed wind was easier than dividing 4 mph by 10mph and multiplying by the 10mph drift to get the same answer.
If only worrying about your own wind adjustments, (not calling wind for multiple other shooters) is there a downside to doing it that way?
Just reporting back in on the results... I scored 11 points higher than my first match. I know it does not sound like much but the COF was harder so I am on the right trajectory! Thanks all!
I want to mention that lots of folks were surprised I was shooting a 16.5 in barrel. The general consensus is "get a new (longer) barrel" & "upgrade you Hunter 700 stock". Most guys I talked to would agree the short barrel 308 in a Hunter 700 stock is a handicap esp as the wind picks up and the range goes 800+
I would like to go chassis for flexibility... way to many options! I have looked at the XLR and the KRG Whiskey 3 but I have a possibility to get a slightly used J Allen which is the JAE 700 I think.
Cheers!
I knew I would get one of you to follow the true method of wind calling, hahahahahahaI just shaved my entire body and went shooting naked, my wind call is now within .5 mph? thx mike
Yes he did. wasnt clear on that.The Gunwerks Questions are good,
If you have to break out a calculator you already lost, plus the Constant he is using is from the old USMC Formula, however that Constant is for a 168gr 308, vs a 6.5, now depending on the size of the target etc, it will work. Based on the caliber and video he hit but on the left so he held too much by a touch. Not knowing target size we can't figure out if .4 or .3 would be better?
There are easier rules of thumb as well like the British Method for quick in your head stuff.
British Method
10MPH wind is your base wind.
1 MOA @ every 100 yards
Wind MPH 2-3 MPH = light, 5MPH = medium
10MPH = base, 20MPH = heavy
Example
Range 600, velocity 10mph = 6 MOA
Range 600, velocity 5 mph = 3 MOA
Range 600, velocity 2-3mph=1.5 MOA
Range 600, velocity 20 mph = 12 MOA
But the video was simple and worked. If you actually run the formula backward to fix the constant. you get,
.4 Wind (bring him back into the center a bit)
35 / 1.4 (MOA conversion)
25 for a constant which fixes the problem.
It's a good simple video, he explains it fine, but he missed the fact the constants are bullet specific.
I have a long way to go. Just when i think I’m getting it, I’m confused again. ??Much simpler to say," My bullet is a 6, and the wind is a 6, so the hold would be 0.5 mil, but that angle makes it 0.4 mil......bang.....ding"
I'm sorry if I confused you, the post you quoted from me is a bit cryptic. The video is of a gentleman using the Army method which as you see, requires a bit more math process and a known constant to arrive at the hold.I have a long way to go. Just when i think I’m getting it, I’m confused again. ??
I'm sorry if I confused you, the post you quoted from me is a bit cryptic. The video is of a gentleman using the Army method which as you see, requires a bit more math process and a known constant to arrive at the hold.
My comment was a bit of mental shorthand, contrasting it to my thought process using the BC method on the same problem.
I can't get into that link.
I can't get into that link.