Rifle MPH

[L3arnette]

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]

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

 

[Deleted member 113831]

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."

 

[isofahunter]

I think like @Skookum.

 

[seansmd]

and when we share wind holds we shouldn't share I held 1.5mil left, it should be I held for a 10mph. That way I can do the math for my MPH gun. Your Grendel hold tells me nothing about my creed.

 

[L3arnette]

@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!

 

[hlee]

I have a sheet of paper that has all my holds on it, so I don't need to remember anything. I'll do the math based on what I think the wind is doing, then like everyone else, I'll hold edge of plate... ?‍

 

[Sincerd]

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

 

[Deleted member 113831]

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.

 

[Sincerd]

So strelok pro can tell you mil per mph at 100 then just multiply by PHY or PHM?

 

[Luvman]

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.

 

[Sincerd]

Simple... I like it

 

[M8541Reaper]

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

^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]

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?.

 

[Deleted member 113831]

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.

 

[Sincerd]

Just like you may be shooting at 680 instead of 700 eh?

 

[Spooky68]

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]

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]

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.

 

[_Raining]

Can something similar work for MOA?

 

[Luvman]

Can something similar work for MOA?

Me No Habla Em oh aye

 

[Tokay444]

Can something similar work for MOA?

No. Get with the now and shoot in mils.

 

[seansmd]

Can something similar work for MOA?

Haha, all the kidding aside, once you have solid dope adjust your calculator 9 o'clock wind speed until you get a easy math multiple of MOA for each 100y increment.

Then sell all your moa shit and buy MIL and be happy. ?

 

[Secant]

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]

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.

 

[Jack Master]

Try this if y'all are still confused.

 

[L3arnette]

Try this if y'all are still confused.
View attachment 7272085

Jack, that is perfect, thank you so much!

 

[thexman]

So I went to JBM using their calculator got this at 5mph wind.

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

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

 

[Jack Master]

So I went to JBM using their calculator got this at 5mph wind.
View attachment 7289953

then I started tweaking the wind speed down to 3.5mph, I got this:
View attachment 7289954

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

You got it bud.

 

[thexman]

You got it bud.

Thank you, sir.

Then I guess using different ammo with different B.C. and bullet weight will change the MPH of the same rifle right?

 

[Jack Master]

Thank you, sir.

Then I guess using different ammo with different B.C. and bullet weight will change the MPH of the same rifle right?

Yes it will.

 

[Deleted member 113831]

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]

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.

 

[Deleted member 113831]

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]

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.

 

[CraigG1]

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