Rifle MPH

L3arnette

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Dec 23, 2019
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Hey guys,

I've just gotten into the podcast and long range shooting. I've heard over and over about your "rifles MPH" and the simplified math going into your wind calls. While it is now 2020 and I have a phone to do all the math for me. I was wondering if someone could explain this to me. I always seem to find that technology fails when I need it the most. Thank you again for any help.
 

hlee

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  • Jul 14, 2012
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    The idea is to find the wind mph that makes your wind holds line up in 0.1 mil per 100 yards.

    For example, my 6.5 creedmoor is a 6 mph gun, shooting 147gr eldms at 2700 fps. This gives me 0.1 mil per 100 yards out to 900 yards.

    My 6.5 Grendel is a 4mph gun shooting 123 gr eldms at 2550 fps. This gives me 0.1 mil per 100 yards out to 800 yards.

    It simplifies what you need to remember, and makes the math easier.

    What's the wind hold in a 10 mph wind at 600 yards for the Grendel? 10 = 4x2.5 so, it is 2.5x0.6 = 1.5 mil.

    For the creedmoor? 10= 6 x 1 2/3 so, it is 0.6 + 0.4= 1 mil
     

    Skookum

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  • May 6, 2017
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    While what hlee wrote is absolutely correct mathematically, the thought process for me goes like this:

    Using his 6.5 Creed (a 6mph gun), I would say this to myself:

    "The range is 600 yards...so right off the bat I start with 0.6mil wind hold...but the wind is 10mph instead of 6mph...so I double it and back off a bit. So 1.2mil ...back off a bit to 1mil."

    With the Grendel (a 4mph gun):

    "The range is 600 yards so automatically I think 0.6mil...but it is 10mph, so double it to 1.2mil and add half again 1.5mil."
     

    L3arnette

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    Dec 23, 2019
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    @hlee Thank you so much for that. It was a really simple explanation and gave me just what I needed. @Skookum Thanks for putting that into a thought process that made sense to me in an actual scenario. Thanks boys!
     
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    Sincerd

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    Dec 29, 2019
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    The idea is to find the wind mph that makes your wind holds line up in 0.1 mil per 100 yards.

    For example, my 6.5 creedmoor is a 6 mph gun, shooting 147gr eldms at 2700 fps. This gives me 0.1 mil per 100 yards out to 900 yards.

    My 6.5 Grendel is a 4mph gun shooting 123 gr eldms at 2550 fps. This gives me 0.1 mil per 100 yards out to 800 yards.

    It simplifies what you need to remember, and makes the math easier.

    What's the wind hold in a 10 mph wind at 600 yards for the Grendel? 10 = 4x2.5 so, it is 2.5x0.6 = 1.5 mil.

    For the creedmoor? 10= 6 x 1 2/3 so, it is 0.6 + 0.4= 1 mil

    How do you get the formula on if your gun is 4 / 5 / 6/ 7 mph gun?

    Where are you getting the other numbers from?

    Say say with 10 = 4x2.5

    Your saying you divide 10 ÷ 4 = 2.5? So the. 2.5x.6. Wheres the .6 come from?

    Just trying to figure this out
     

    Skookum

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  • May 6, 2017
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    How do you get the formula on if your gun is 4 / 5 / 6/ 7 mph gun?

    Where are you getting the other numbers from?

    Say say with 10 = 4x2.5

    Your saying you divide 10 ÷ 4 = 2.5? So the. 2.5x.6. Wheres the .6 come from?

    Just trying to figure this out
    The .6 comes from the range being 600 yds. 0.1 per 100 yards, so 600 yards = 0.6 mils.

    Using your ballistic app, you find the wind that gives you 0.1 MIL drift per 100 yards. This is the MPH of your gun/ammo combination.

    There are a couple ways to do this. Some prefer to line everything up at 600 or 800 yards, realizing that most shots will be within this distance. They then add an extra 0.1 mil at 900 or 1000 yards if the shot is in that range.

    The original way was to line this up at 1000 yards, and accept the fact that there will be a minute difference at closer distances, but being closer, matter much less.
     

    Luvman

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    How do you get the formula on if your gun is 4 / 5 / 6/ 7 mph gun?

    Where are you getting the other numbers from?

    Say say with 10 = 4x2.5

    Your saying you divide 10 ÷ 4 = 2.5? So the. 2.5x.6. Wheres the .6 come from?

    Just trying to figure this out
    You have to figure out what MPH wind your rifle has .1mil per 100yd windage hold

    example my 18” .308 shooting a 185gr juggernaut at 2525 FPS is a 5mph gun to 700 yds because 5MPH 90* wind holds are .1@100, .2@200, .3@300, etc, etc to .7@700.

    The math comes in after you know what MPH your rifle is and what MPH your wind call is.

    if I was shooting at my .308 500yds and have a 10 MPH wind. I know at 500yds for a 5MPH wind I hold .5 so for 10MPH I would hold 1mil. (Double my 5mph hold)

    If I were shooting at 700yds with a 3MPH wind My hold would be .4mils because my 5mph hold at 700 is .7 and 3MPH is a little over half of 5MPH so would take half of my 5MPH (.35mils) and round it up to .4mils.
     
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    M8541Reaper

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  • Jul 23, 2011
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    How do you get the formula on if your gun is 4 / 5 / 6/ 7 mph gun?

    Where are you getting the other numbers from?

    Say say with 10 = 4x2.5

    Your saying you divide 10 ÷ 4 = 2.5? So the. 2.5x.6. Wheres the .6 come from?

    Just trying to figure this out
    FE182857-31CD-4B72-A256-A8921810D11D.jpeg
    ^For a 5mph gun.
    Input all of your data into your calculator, turn off spin drift, and adjust your full value wind inputs until your tenth mil hold value is reflective of your distance.

    I do it like shown above but others tailor their MPH info for the farther ranges.

    if I have a 5MPH wind and I’m shooting at 500yds, I use .5 mils.
    If I have a 10mph wind at 500 yds, I use 1 mil.
    if I have a 15 mph wind at 800yds, I’ll use 2.4 mils.
    All other speeds can be broken down quickly in your head, just as you do when getting change back at a register.

    The MPH method, combined with the use of the modern wind rose (that’s floating around here), makes wind calls super fast and effective.

    does that make sense? It’s one of those things where you’re like “wtf is this?” But as soon as it clicks you’re like “holy shit why haven’t I been doing this all along?!”
     

    Snuby642

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  • Feb 11, 2017
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    Your rifles all suck.
    I went to the range today and my rifle and I got to 45 mph.

    The bad part was it is still short stroking

    Relying on others to make wind calls in a competition, hummmm?.
     
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    Skookum

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  • May 6, 2017
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    So strelok pro can tell you mil per mph at 100 then just multiply by PHY or PHM?
    Not exactly. The mph needs to be done further out to avoid a compounding error. This isn't that exact. When we say 0.1 mil per 100 yards, we are speaking of an average.

    Wind deflection is parabolic, just like trajectory is parabolic. However with wind, the difference between that arc and the straight angle while a round is supersonic, is inconsequential enough that we don't notice as long as we are using an average gleaned from distance.
     

    Spooky68

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    Aug 24, 2014
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    Oh hell... now I get it. I never did understand the mph gun designation and how to get it. I am sure it was discussed in the podcast and the online discussions subsequent to it but I must have missed or ignored it and gave up. I swear I don’t know how I made it past 2nd grade.?
     

    Dunraven

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    Feb 1, 2019
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    How do you get the formula on if your gun is 4 / 5 / 6/ 7 mph gun?

    Where are you getting the other numbers from?

    Say say with 10 = 4x2.5

    Your saying you divide 10 ÷ 4 = 2.5? So the. 2.5x.6. Wheres the .6 come from?

    Just trying to figure this out
    My understanding is you start by finding out the G1 value for your bullet. If it's, say, .521 for example, you have a 5MPH rifle. Don't ask me why that works, but it seems to.
     

    seansmd

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  • Aug 8, 2018
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    My understanding is you start by finding out the G1 value for your bullet. If it's, say, .521 for example, you have a 5MPH rifle. Don't ask me why that works, but it seems to.
    That's a good starting point, in the end you need real world solid dope and a balistic calculator that you have tried up to your dope, make sure AJ and spin drift turned off and minimized. Then add 9 o'clock wind speed until your 100y increments line up with 0.1mil increments. My 6.5CM is a 6mph and from 100-700 it lines up nicely.Screenshot_20200308-174405_BallisticsARC.jpg
     

    Secant

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    Aug 11, 2019
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    Can something similar work for MOA?
    Yes. There seems to be two 'typical' methods: determine the wind MPH to correlate to either 0.25 MOA per 100 yards or 0.5 MOA per 100 yards. If you go the 0.25 MOA per 100 yards, you 'count' in quarters (harder for some than others).

    If you go with the 0.5 MOA/100 yards route, that correlates to the range by 1/2. For example, say you have a 8 mph gun:

    Range is 600 yards with a full value 8 MPH wind, correction is 3.0 MOA (6 / 2 = 3.0)

    I have and use mrad and moa scopes - dimensionless angular units are a lesser issue than they are made out to be on the internet. If the dope is dial/hold 7, then dial/hold 7......just my opinion of course.
     

    Jack Master

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    Can something similar work for MOA?
    MOA Version.
    100yds - 0.50 moa
    200yds - 1.00 moa
    300yds - 1.50
    400yds - 2.00
    500yds - 2.50
    600yds - 3.00

    When on the range this math is quick because it's 1/2 of your target distance.

    This moa version will typically have a higher gun mph than the mil system, about 1/3 more mph than the mil version. It's important to recognise this so when someone says they have a 9mph 6.5 creed we know it's in moa.

    Here is my 6.5 creed in each system.
    Mil = 6mph gun
    MOA = 9mph gun

    If you play with the linear numbers at a target distance you will see this is the same horizontal deflection in inches.
    Example: Target at 500yds. Wind is 9 mph
    MOA = 2.5moa wind call = 13 inches at 500yds
    Mil = 0.75mil wind call = 13.5 inches at 500yds.
     
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    sonichanxiao

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    Dec 24, 2018
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    So I went to JBM using their calculator got this at 5mph wind.
    JBM1.JPG

    then I started tweaking the wind speed down to 3.5mph, I got this:
    1585972131213.png

    So now, I can say my rifle is a 3.5mph gun. correct?
     

    Skookum

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  • May 6, 2017
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    Yes it will.
    Great charts Jack. :)

    Just to simplify the mental process @L3arnette , @sonichanxiao ....when you find the distance to target, you immediately think of the standard wind call for that distance. That standard wind call is the anchor to get the process started.

    So no matter what the wind is, if the target is at 900 yards, I immediately think 0.9mils (if using mils). I then do a quick mental calculation. Say I have a 4mph gun, but the wind is 6mph. I know that six is half again bigger than 4, so I just think 0.9 + another half (0.5), and hold 1.4mils and pull the trigger.

    Same in Moa, If 800 yards, I would immediately think 4moa and modify from there. If I have a 9mph moa gun, but the wind is 7mph, I just think 4moa less a 1/3 and hold 3moa.
     

    goatboy

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    Great discussion, thanks.

    This approach seems like the wind dots in a tremor3 reticle, but lined up with mil marks as opposed to .9 something value.
     

    Skookum

    Jack Booted Thug...Crushing the American Dream
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  • May 6, 2017
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    Great discussion, thanks.

    This approach seems like the wind dots in a tremor3 reticle, but lined up with mil marks as opposed to .9 something value.
    Yes, it is exactly like the wind dots.

    This method is an evolution of the BC method, and goes back to the late 1990's.

    Todd Hodnett didn't invent it. He had never heard of it till about 2004-2005. He just was the first one to monetize it.
     

    Steel head

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  • Aug 3, 2014
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    Great charts Jack. :)

    Just to simplify the mental process @L3arnette , @sonichanxiao ....when you find the distance to target, you immediately think of the standard wind call for that distance. That standard wind call is the anchor to get the process started.

    So no matter what the wind is, if the target is at 900 yards, I immediately think 0.9mils (if using mils). I then do a quick mental calculation. Say I have a 4mph gun, but the wind is 6mph. I know that six is half again bigger than 4, so I just think 0.9 + another half (0.5), and hold 1.4mils and pull the trigger.

    Same in Moa, If 800 yards, I would immediately think 4moa and modify from there. If I have a 9mph moa gun, but the wind is 7mph, I just think 4moa less a 1/3 and hold 3moa.
    This is kinda how I’ve doing it
    Find needed drop and assume a 8 mph wind.
    Then before shot modify the wind value,,,12 mph wind,,, Add 50% more hold.

    I’ve also started playing with modified MPH value brackets for further distances (1000+) that Jack brought up in another thread.
    It’s not perfect but it gets me in the ballpark easily and I’ve gotten some surprising first round hits in some pretty substantial winds this last month using it.
     
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    CraigG1

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    better late than never ... fantastic information ..... thanks so much for sharing