Surprised me, popnfresh . . . you love to test things lol.

Anyhow, my own tests led me to believe it functions a bit like a barrel tuner. Attach it in the same spot on the barrel with the same strap tension you get the same POI shift as last time. Change either parameter slightly and I got a different shift.

All tests I ran were from the 6 o'clock position (determined freehand) - never thought of muzzle blast deflection.

All shifts during my 2-barrel test were generally  toward 10:30 o'clock.

Harder to prove . . . with reasonably small changes in those two parameters the magnitude of the POI shift changed, but not it's direction.

The POI shifts for one heavy barrel (eg Bartlein 26" MTU) were smaller than one lighter barrel (Rem 700 24" in whatever the hunting contour was 50 years ago).

Small group size shifts are tough to prove . . . or disprove . . . but clearly (to me at least) any subtle change in the attachment or its location can produce a different POI shift. Who needs to add that kind of variable during load development? Others of course can choose differently, and I'm sure do.

I recorded readings with my Magnetospeed several weeks ago that just didn't make sense.  They were 500-1000fps off from my load data and readings were inconsistent.  

I either had the sensitivity wrong, or I didn't have it parallel to the barrel.  I hope, anyway.  I will need to get out and try it again.  

Labradar is on my shopping list.  Come on Black Friday deals!!!!!!

I am surprised that there have not been clones of both pieces made available. I do want a LabRadar after seeing one used.

Were you shooting bi-metal jackets? I messed up last weekend when I got out  the AR to compare Magneto to Labradar with Wolf ammo , numbers were all over, I forgot to change the trigger to magnetic jackets.

My 20" MTU .308(168-230gr) shows no noticeable group size change or poi shift. I  may have thought there was a little once in a while but the effect was small enough to just be error on my part or change in powder temp.

My 18" .223 AR(55-90gr) shows 2-3moa poi shift but no noticeable group size change.

My 24" 6.5 Grendel AR(140-147gr) shows about 1moa poi shift and groups change as well.

Now the ARs are .75" diameter at the muzzle the .308 is 1" diameter at the muzzle so the bayonette is 1/8" closer to the bore on the ARs, which have more shift.
The ARs are also shooting much lighter bullets.....so I kind of thought they are easier to "push" away maybe.

I thought maybe the 24" had a group size change because the 24" barrel is less stiff and maybe more effected by the "tuner effect".

Without actually doing a test, I half assed concluded that the weight of the bullet and distance the bayonette is from the bore effected the POI shift. 
... and the stiffness of the barrel determined how much the bayonette would effect group size. I didn't really think too much about it, so I  could be way off, just some observation from a very small sample.

Lol therefore......I'm not sure that mounting the bayo to the stock would solve the poi shift problem.

I'm still going to try it

Yeah, I am only speculating. It will certainly solve the barrel harmonics issue.

I'll let you know how it works out
worst case, I figure I still have another chronograph to play with

Today I tried the Magnetospeed at 3:00, 6:00, 9:00, 12:00 and the point of impact shift was clearly related to the rotation of the bayonet.
This suggests that the point of impact change is not from harmonics but from the bullet flying close to the surface of the sensor.

From 3:00 to 9:00 there was a shift of 1.18 moa horizontal(away from the bayonet)
From 6:00 to 12:00 there was a shift of 0.14 moa horizontal


From 3:00 to 9:00 there was a shift of 0.25 moa vertical
From 6:00 to 12:00 there was a shift of 1.24 moa vertical(away from the bayonet)


From center of POA(actual zero poi)without bayonet

3:00- left 0.45moa.... up 0.33moa shift
9:00-right 0.73moa.... up 0.57moa shift


6:00- rt 0.22moa.... up 1.23moa shift
12:00 rt 0.37moa..down 0.01moa shift

that is seriously interesting stuff

it got me thinking about maybe modifying a Houle Tube.  I dunno, I'll play around with it

not like I have anything better to do

thanks for the info

The data certainly suggests that rotation of the bayonet is a significant factor.

Going with that . . . then POI shift may also vary with slight deviations in the MS's centerline either horizontally or vertically (or is that pitch and yaw lol) from the centerline of the bore.

you guys see that magnetospeed rig that david tubb made? basically just mounted it on an arm attached to the rail of the rifle that reaches out to the muzzle.

snipers hide had him on a bit ago, you can see it in the video.

https://www.youtube.com/watch?v=6C7ZXS7MrKc

I saw that and was thinking of trying to do that for a while before I saw the video
a lot of others have tried to do the same, but in some pretty janky-sketchy ways

not drinking the Tubb koolaid or anything, just wanted a way to measure from a field rifle in-use
after reading pop's comparison data on the labradar and magnetospeed I was second-guessing the idea
but I already ordered the metal and hardware, may as well mill it up, try it out, and see where it goes

worst-case scenario, I'll have a really quick way to mount the magnetospeed in a manner that's indexed to the rifle

To be clear, I think that mount will work for load development with the intent removing the barrel harmonics from the process.

I just question the ability to zero with it on the rifle, which is the main reason I got the Labradar. I can get muzzle velocity and zero data with the same rounds fired.

In my ONE test, the group size didn't change for all five groups(4 positions and 1 without the bayo) outside the capability of the load. 
This was on my 20" MTU profile rifle which is least effected by the bayonet.


I have a bunch of shit to try out this weekend but if I have time I'll try the rotation thing on my 24" AR ( if the scope allows it in the 12:00).

This is all good information brother, but even in your small test and with such strong numbers showing variation I'm more prone to understand it as "being pretty damned likely" if not outright "gonna happen" data

I'm trying to determine a manner in which I could mount a magnetospeed to the end of a barrel with consistency in mind.  I'm almost done with the original lateral support mount now, much like Mr Tubb's design, and I'm moving toward making another that uses a modified bloop tube with the magnetospeed mounted near-flush with the interior dimensions of the tube.

this is all just for fun, but wouldn't it be nice if I could tell the actual velocity during field-fire?  the labradar is awesome, I've used one at work a bit and I'm in love.  But the size and weight are real downers in a practical environment
the end result could very well look like a small and thin suppressor with the sensor mounted along the long axis of the tube, who knows?

in the end I'm just fucking around and learning a little bit.  I never really learned anything by staying inside the box

in the mean-time I'm still thinking about "if we could manage to discount the magnetism of the barrel, could we mount a magnetospeed directly to the barrel exterior and gather data?"  maybe a way to zero the sensor to the barrel or make a stronger sensor to overcome the inherent magnetism of the barrel?  that would be wild

I mean, in the end we're just talking about sensitive voltage detectors (probably Hall Effect sensors), right?

I have a strain gage mounted on my .308 for my PressureTraceII. That would make a pretty good switch to start a timer, then maybe a muzzle brake with a sensor( like the magnetospeed) to stop the timer. That wouldn't mess with the barrel at all that way. 

My biggest complaint with the LabRadar is the interface.  It's not very intuitive, and requires you to break position and reach out to touch the buttons all over the face of it.  Some of the buttons are positioned at so much of a moment-arm from the mount, that it can easily mess up the alignment in all but the strongest mounts - and even then.  It's really a first generation attempt at an interface.

Once they get the Bluetooth option working, that will fix much of that problem (I hope).  But that's been a work-in-progress for quite some time.  There have often been rumors that it's just about to be released for years now, but so far, none have materialized.  It's really a shame, because for such a hands-off system, it has potential to require very little fuss to work with, but that interface is really bad.

I'm excited about this idea, but I really can't explain why.  Mostly because it can only spell frustration, expense, and headache for me.
After some thought, mounting Hall Effect sensors would make more sense, they're cheap (like, $3 each) and they can be used with a lot of different plug-play electronics systems.  I already ordered a dozen for an Arduino kit, gonna play around with that.  But using a stress gauge to measure would mean that we're measuring shock at one end and speed at the other.  It would remain more accurate to measure speed-speed, your thoughts?

the mount has experienced a setback though.  I crashed my mill head while cutting a circular hole with my turntable vise.  
Waiting on new tooling, bought a pair of boring head sets for spares in case I fuck up again.

No, my thinking is the strain gage would  be used as a simple switch to start a timer, then at the other end the muzzle device with the hall effect sensor to stop the timer. So it will calculating speed by the time it took to travel the given distance..... The hall effect sensors couldn't just be placed on the outside of the barrel like the strain gage can...can they? I don't know much about them.


..... Of course the bullet accelerates as it goes down the barrel so I guess you wouldn't want it at the chamber. I guess closer to the muzzle.

So you have 5" or so from the muzzle device with the hall effect sensor, your timer/computer/gizmo is going to have to figure out how much acceleration there was is in that 5" of travel down the barrel.



Sounding more and more like this idea won't work, 5" of barrel acceleration can be quite a bit and quite different  with different setups I would think.

Maybe it could be calibrated to the load with another, less mobile chronograph. ....
Say the sensors measured 0.25 milliseconds to travel 5", so you tell it the Labradar measured 2600fps, at 0.3 milliseconds tell it the speed was 2580fps and so on so it can "learn" that load. 

Don't know how accurate that would be....


I think your blooptube is probably the easiest to get working. Even if there is a POI shift from the bayonet you can just zero with it on or put the shift amount into your ballistic solver.

Just to add to this, I did the same test with my 24" 6.5G AR using 90gr TNTs, much more shift with this.


From 3:00 to 9:00 there was a shift of 3.32 moa horizontal(away from the bayonet)
From 6:00 to 12:00 there was a shift of 0.30 moa horizontal


From 3:00 to 9:00 there was a shift of 0.12 moa vertical
From 6:00 to 12:00 there was a shift of 4.11 moa vertical(away from the bayonet)


From center of POA(actual zero poi)without bayonet

3:00- left 1.30moa.... up 0.1moa shift
9:00-right 2.02moa...down 0.02moa shift


6:00- left 0.08moa.... up 1.87moa shift
12:00 rt 0.26moa..down 2.26moa shift

Maybe this will give you guys some useful ideas:

Two-Box Chrono

And just to be clear, "Twoboxer" has nothing to do with this device :)

I'm quite happy with the Labradar, don't care to dink around aligning sensors ever again.

Bryan Litz uses acoustic sensors for measuring BCs. 
Now Litz claims to use the Labradar for all testing outside of the lab, I wonder why he doesn't use his acoustic setup(PITA maybe)? Guess I'll have to wait for his next book.

This is semi-on/off topic, but regarding the Labradar - I received this blurb in an e-mail today (08/31/2017) from Labradar:

LabRadar Bluetooth App Coming Soon!

The Bluetooth app will allow users to control the LabRadar device remotely from your phone or tablet, let you export your data files, and many more features to be announced soon. We do not have a firm release date at this time, but if you register your LabRadar at www.mylabradar.com you be notified when the firmware is available.

You go girl.......

Anybody on the fence Brownells has $70off and free shipping on orders of $600. That is a hell of a deal. Code "M6V" expires 9/3

Sure you can find $41 worth of goodies to get you to $600.