# What is the "McDonald/Almgren approach"

Discussion in 'Long Range Hunting & Shooting' started by Hired Gun, Nov 24, 2006.

1. ### Hired GunWell-Known Member

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What is the \"McDonald/Almgren approach\"

What is the "McDonald/Almgren approach"

I was recently informed that using the cosine math factor for correcting the true horizontal distance was flawed and that the "McDonald/Almgren approach" would be more accurate. So much better that it may be the difference of me missing with my method and a hit with that method.

I agree that only considering the cosine corrected yardage may be flawed by the fact it doesn't account for time of flight which I believe at really long range like 2000 yards at a really extreme angle it must have some affect. example: 2000 yards at a 95 degree angle verses 200 yards at the same 95 degrees. It's hard to believe that the exact same cosine correction fact would apply.

Any comments on the subject would be appreaciated.

2. ### Brown DogWriters Guild

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Re: What is the \"McDonald/Almgren approach\"

I believe those 2 names (well McDonald at least) are the fellows who wrote the inclined fire calculations for Sierra infinity.

I posted this some time back on a different website...here's a copy and paste of the content, hope it maybe of some use:

The 'base line' method, although used by many is actually the least accurate way of using your cos measurement...because it has absolutely nothing to do with the ballistics of what's going on in inclined fire!

Far more accurate is to multiply the comeup you would have applied for your laser distance by the cos of the angle.
This does reflect what is going on ballistically ...the bullet has the same TOF to a given target regardless of angle of fire...it therefore drops the same amount regardless of angle of fire (it doesn't magically drop less!)...what changes is your perspective to that drop (and therefore the apparent shape of the trajectory).
Hold a pencil vertically in your hand at arms length (with your arm horizontal); lets say the pencil length represents your bullet drop at 1 arms length.
Now drop your arm to 45deg, but keep the pencil vertical.
The pencil appears shorter, even though it has remained the same length ....ie the drop has remained the same, but less drop is apparent because of your perspective. How long does it appear to be? multiply it's actual length by the cos of 45deg...just the same as multiplying your laser range comeup by the cos of the angle!

Here's a link to a link on the ACI site where all this is explained by one of the Sierra Infinity software designers [McDonald]:

http://www.snipertools.com/article4.htm

Only read this bit if you're a ballistics nerd: The software engineer concludes that a set of rather complicated calculations based on actual bullet drop (rather than simply comeups) are somehow yet more accurate again (this is the method he uses in the Sierra program)...he tests his theory by comparing the results of this type of calculation against his Sierra outputs...they are close to each other so he concludes greater accuracy...what he fails to point out / realise is that both the calculation method and his software method are the same...of course they'll be close!! ...nothing proved!

...unless a ballistic prog goes into a full vector analysis of how gravitational acceleration is affecting bullet velocity throughout its time of flight (and therefore calculating the minute changes to TOF at varying angles of projection)(ie 'straight up' it will directly slow the bullet, 'straight down will speed it)I believe the only greater accuracy from a basic ballistic prog comes from the fact that 'comeups' represent data that has been rounded-of to the nearest click value, if you use that and then round-off the result..the answer will be slightly less accurate than precise raw data that has only been rounded off once.

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4. ### BuffalobobWriters Guild

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Re: What is the \"McDonald/Almgren approach\"

What most people use is method number 1

What most people should use is method number 2

What a good ballistics program will do for you is Method Number 3 - the McDonald and Almgren calculation.

5. ### BuffalobobWriters Guild

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Re: What is the \"McDonald/Almgren approach\"

As a physicist I will assure you that method Number 1 is not correct according to the fundamental laws of physics. However, it is a good fast simple method that is useful for hunting. Hunting is what most of us do.

You should take note that there is a slight difference in drops going uphill and downhill. Uphill you are fighting gravity and downhill you are going with gravity.

6. ### mikebobWell-Known Member

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Re: big bore

all my targets are 6"-6" the average size of kill zone. by the way my preferred weapon of choice is a bowtech tribute, dead nuts sites, easton carbon arrows, spitfire 100gr, no peep shooting 310 fps. my comp bow is recurve 55lbs no sights maxima arrows. By the way they will not let you fly the jet if you cant fly it without the comp. minus alt &amp; speed meter.