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Magnetospeed Error Correction

 
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Old 03-05-2014, 11:08 AM
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Magnetospeed Error Correction

You guys with the new Magnetospeed chronos. How does it correct for the recoil of the rilfe? A 9 lb 30-06 will be moving backward (and taking the Magnetospeed with it) as the bullet is leaving the barrel. The velocity of the rifle at that point in time (just before the velocity of the bullet is measured) will be about 9 feet per second and the rifle will have moved backward about 0.060 of an inch (basically in free recoil since it hasn't compressed the recoild pad or the flesh of your shoulder). This velocity will get added to the velocity that the Magnetospeed is reading. Does the unit allow you to tell it the velocity of the rifle so it can be automatically corrected?
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Old 03-05-2014, 11:13 AM
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Re: Magnetospeed Error Correction

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Originally Posted by Engineering101 View Post
You guys with the new Magnetospeed chronos. How does it correct for the recoil of the rilfe? A 9 lb 30-06 will be moving backward (and taking the Magnetospeed with it) as the bullet is leaving the barrel. The velocity of the rifle at that point in time (just before the velocity of the bullet is measured) will be about 9 feet per second and the rifle will have moved backward about 0.060 of an inch (basically in free recoil since it hasn't compressed the recoild pad or the flesh of your shoulder). This velocity will get added to the velocity that the Magnetospeed is reading. Does the unit allow you to tell it the velocity of the rifle so it can be automatically corrected?
In a test this past summer shooting a Magneto against an Oehler 35, the Magneto was within a few FPS of the Oehler with 4 different rifles. Based on that, I would assume recoil has little to no effect.
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Old 03-05-2014, 11:19 AM
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Re: Magnetospeed Error Correction

Bullet moving 3000fps in one direction, rifle 9fps in the other. Works out to an error less than a third of a percent. Big whoop.
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Old 03-05-2014, 11:27 AM
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Re: Magnetospeed Error Correction

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Originally Posted by Engineering101 View Post
You guys with the new Magnetospeed chronos. How does it correct for the recoil of the rilfe? A 9 lb 30-06 will be moving backward (and taking the Magnetospeed with it) as the bullet is leaving the barrel. The velocity of the rifle at that point in time (just before the velocity of the bullet is measured) will be about 9 feet per second and the rifle will have moved backward about 0.060 of an inch (basically in free recoil since it hasn't compressed the recoild pad or the flesh of your shoulder). This velocity will get added to the velocity that the Magnetospeed is reading. Does the unit allow you to tell it the velocity of the rifle so it can be automatically corrected?
As an engineer, I would figure you would be aware of velocity vs disance traveled. You might ask how that plays into this scenario? Here we go...

The bullet actually leaves the barrel WAY before you even feel the first hint of recoil. If a bullet is traveling 3,000 fps, and your barrel is only 26" long (2.17 feet), then it takes your bullet approximately 0.0007233 seconds to travel the full length of your bore and out of the muzzle, after ignition. Felt recoil will not happen until after the bullet has left the muzzle expelling all of it's gasses and energy into the atmosphere causing a rearward force (recoil).

I've waved my MSv2 bayonet around (while plugged in) to see if it would pickup anything, and I think they've got it set to where it has to have something solid traveling VERY close to it, for it to read anything, so I'd assume you'll be ok. Mine reads perfectly, and is very close to book load velocities on several of my loads, so I would guess it is pretty accurate.
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Old 03-05-2014, 11:29 AM
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Re: Magnetospeed Error Correction

if you watch a shot in slow motion you will see the bullet is gone then the recoil happens .
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Old 03-05-2014, 11:37 AM
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Re: Magnetospeed Error Correction

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Originally Posted by ksubuck View Post
Bullet moving 3000fps in one direction, rifle 9fps in the other. Works out to an error less than a third of a percent. Big whoop.
What he said.
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Old 03-05-2014, 11:50 AM
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Re: Magnetospeed Error Correction

MontanaRifleman

I assume you are saying that the numbers on the displays of the two chronos closely matched. That is very interesting. I would expect that they would not match because there is velocity loss from the end of the barrel to a conventional chrono of about 7 fps (depending on bullet BC and how far down range you put the sky screens) so a conventional chrono should always read slower than a magetospeed which is right on the barrel. And for the reasons I stated above, the magneotospeed should read fast by about the same amount (depending on rifle recoil). Sooooo… when everything is working right the magneto readout should be about 15 fps faster than the conventional chrono. Did you take this correction into account when you say the chronos agreed with each other?



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What gave me away? I knew I should have picked a different login right after I pushed the button. Yes I was a engineer – and now I’m just an old and senile gun nut.

You are of course correct when you say the bullet leaves the barrel way before you feel any recoil. In fact the rifle has moved about 0.060” backwards at that point, which on a human scale is essentially zero. It does however have a velocity of about 9 feet per second due to the equal and opposite reaction thing. I was just wondering how the magneospeed dealt with that.
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