Magnetospeed V2 chronometer

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Re: Magnetospeed V2 chronometer

Postby Al in Mi » Thu Aug 06, 2015 4:23 am

The Lab Radar unit has me intrigued but man-o-man ouch on the cost.
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Re: Magnetospeed V2 chronometer

Postby Hoot » Thu Aug 06, 2015 5:50 am

ARconnect wrote:...i snip.. I wonder if you would hazard a speculation as to why the use of the Magneto would change a bullet's POI - especially if it occurs primarily in the upward direction. I understand that attaching anything to a rifle's barrel can, and likely will, change its resonance. That's why we free float barrels. And we work up loads to find the sweet spot in the barrel's resonance....snip...
Any thoughts?


Varmint Al has several web pages that explain barrel resonance, deflection and the effect of a muzzle device on the end of it. That device can be in the form of a tuner, flash hider, brake and yes the Magnetospeed chronometer.

I love shooting .22 Rimfire Benchrest. That was what I was doing yesterday evening as a matter of fact. We had dead wind conditions and I wanted to do some tuner experiments. When the barrel is tuned just right, varying the length by virtue of the adjustable tuner, only +/- .025 inches can result in the .22 bullet POI at 50 yds varying almost an inch vertically. Admittedly, at the power of a .22 and the poor BC of the bullet, it doesn't take much to make it deviate, but the same principle applies to all rifles, regardless of caliber and distance to the target. Geometry being what it is, obviously the closer the distance to the target, the less the net impact.

If you haven't tried this, remove your brake and see what happens to the POI. That's not because of greater recoil. The brake acts upon the recoil after the bullet exits the muzzle. The impact upon the bullet's flight path happens as it races down the barrel and the barrel energy impulse ahead of the bullet makes the barrel deflect before it clears the muzzle. Better yet, put some PTFE tape on the muzzle's brake threads and screw it all the way on. From a repeatable positioning rest, take a shot. rotate the brake one revolution and take another shot. Repeat several more times as you screw the brake out one revolution at a time and watch the POI shift. In theory, there should be a sweet spot for the brake position that enhances the vertical POI dispersion that is a function of variation in load velocity. All that is well and good on calibers that are small in relation to your barrel's diameter. Like shooting a cannon, vs a mortar. There's a good chance that the mortar-like trajectory of the 450b will cause it to respond less to muzzle harmonics. I've shot sub-MOA 5-shot groups at 100 yds with the 450b and had velocities vary by 100fps or more yet very little vertical stringing. I'm off on an accuracy tangent. Check out Varmint Als web site if you get the time. It cool stuff.

Hoot
In Theory, there is no difference between theory and practice. In Practice, there is.
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Re: Magnetospeed V2 chronometer

Postby ARconnect » Fri Aug 07, 2015 12:39 am

Thanks guys, I appreciate your assessments and the great resources.
ARconnect
From the Land of the Bullet Button, 10 Rnd Max Cap Mags, and Lead-Free Fodder. But this place would be Paradise without the Politicians.
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