In Defense of Magnetospeed - A Compendium to Set the Story Straight

[Lapua40X]

... the effect on POI seemed to be dramatically reduced when using th Magnetospeed with a muzzle brake, which diverts a significant amount of the muzzle blast ....

Excellent additional data element. One that I had overlooked. Thanks a bunch.
When these discussions end, the logical conclusion usually goes something like this:
Magnetospeed is intended ONLY to provide MV data. It is not and never was intended to provide anything else.
Leaving the bayonet on the rifle for load testing is a bad idea. The shot placement on target is not a reliable indicator of load performance when the bayonet is left in place.
Test the load, test for MV, in two separate steps.
Does that mean using more ammo than we might use with a standard sky screen type of chrono?
Perhaps; but that's not a certainty.
The reliability (or lack thereof) of sky screen chronographs often means shooting more rounds than originally planned because of the unreliability of their performance under certain conditions.

 

[Ned Ludd]

I don't know that it's necessarily a bad idea per se, but one needs to be aware of the effects of having the bayonet attached in order to make an informed choice of whether to use it during load development. Whether it's a good or bad idea will largely depend on the specific requirements of the shooter. When doing load development for my F-TR rifles, I expect somewhere in the 0.25-0.35 MOA precision range and won't be satisfied until that's how the load is consistently grouping. The MagnetoSpeed effects are definitely enough to throw development off at that level of precision. However, someone developing a hunting load as an example, that might be completely satisfied with 0.5 to 1.0 MOA precision, may never notice the effect during load development. So the intended purpose and precision requirements can play a big role in deciding whether to leave it on when shooting for group dispersion.

 

[hogpatrol]

An interesting thread and one which I need to add my authoritative experiences with the MS. I have used one extensively on a variety of rifles, muzzleloaders, shotguns and handguns. Some of the issues I've found with it are that it can:
Cause uneven barrel heat distribution and wear out the last couple inches of the barrel quicker than the throat.
Increase barrel harmonic distributions due to vibratory anomalies at the muzzle aka, "tuner effect"
Negate the effects of a bad crown
Increase the speed of moly coated bullets due to magnetic acceleration as the bullet passes over the bayonet
Velocities reduced due to magnetic pull on copper jackets.
Change shooting spending habits/accelerate wallet wear/credit card usage (which in turn can cause an acute case of SIDS aka shooting induced divorce syndrome.)

Since this is being publicly posted on the internet, it should be taken as gospel. Anyone having different results should re-read the manual and remember to adjust the attaching strap to 15 ft. lbs. of pull, then fine tune the tightening screw another 2.5 lbs. for a total of 17.5 ft. lbs of torque. Anything over 5% difference will cause incorrect readings, your hair to fall out, increase your heart rate and give you indigestion.

 

[rardoin]

One other test to try to determine if the M blast is deflecting off the device and affecting the bullet is to try adding spacers to the stack under the clamp to increase distance from the flight path to the bayonet. Of course the sensitivity would need to be increased but if that reduced the POI change it would further the support of that theory. It matters not to me as I use it to determine the velocity of precisely grouping charge weight and determine the ES/SD and to verify velocity of known loadings for variation.

 

[normmatzen]

gstaylord

You are right on.
But do not underestimate the inductive kick generated when the bullet passes through the inductive magnetic field. It is comparable to a wind blowing on the bullet.and, it will nudge the bullet opposite to the bayo.

And, yes, I'm an electronic engineer.

 

[snakepit]

A couple of years ago I was checking load velocities with my MagnetoSpeed. After shooting my last 4 round group with the MagnetoSpeed installed I decided to shoot my remaining 4 rounds with it not installed on the barrel. I was shooting at 600 yards with my 6mmBR/1.25"x30" Brux Barrel. The load was 30.5 gr of Varget, Berger 105 Hybrids jumped .025 and CCI 450's. I measured the target on my computer using the On Target Precision Calculator Target 2.1 Program. The 4 shot group without the MagnetoSpeed installed measured 1.346" wide by .540" high. The 4 shot group with the MagnetoSpeed installed measured 1.390" wide by .506" high. The group with the MagnetoSpeed installed measured 4.281" down and 1.291" left center to center from the group without the MagnetoSpeed installed. Again this was at 600 yards. I can't tell you why the POI was down and left.

I published this on other MagnetoSpeed threads and I am continually told that this is not statistically significant because I did not have enough groups and rounds per group and will probably be told this again and they are probably right but I did this more out of curiosity than trying to make a factual statement to prove a point. I only use my MagnetoSpeed to check velocities at the end of load development and I have only used it one time to check a group for POI shift comparing the MagnetoSpeed on and off the rifle
at the same testing session.

 

[Ned Ludd]

gstaylord

You are right on.
But do not underestimate the inductive kick generated when the bullet passes through the inductive magnetic field. It is comparable to a wind blowing on the bullet.and, it will nudge the bullet opposite to the bayo.

And, yes, I'm an electronic engineer.

Norm, this is one of the tests I did that I didn't mention in any detail in the previous posts. Using a very high end analytical balance set to read to .00001 g (.01 mg), I performed 20 measurements where I placed a bullet on styrofoam blocks about 12" above the balance pan. At that distance, the magnets in the bayonet did not cause detectable reading via interaction with the steel balance pan. Manually bringing the bayonet magnets into proximity of the bullet comparable to what would be observed in actual use had no effect on the balance reading, either positive or negative. Some may argue about the result of that test, but I'm pretty convinced the POI shift is not an effect caused by the magnetic field. Whether it's shock wave or some gas effect (I referred above to "muzzle blast", which I perceive to include both of those effects), I can't say for sure, but the various tests and observations seem to support one or both of those as the likely culprit for the change in POI.

The changes in group dispersion are relatively simple to explain. I can actually "feel" the device vibrating noticeably during the recoil impulse when I shoot. There is no way that could fail to impact barrel harmonics. I envision the device acting in a very similar manner to a barrel tuner, which obviously affects grouping when adjusted. Again, not a big deal to me, I love the ease of use of the MagnetoSpeed and its reliability. I just don't put any emphasis in groups shot with it attached and shoot those separately from velocity determination. It does mean more time/effort/components for the loaded rounds, but for my purposes, it's also on many occasions an easy way to generate once-fired brass while also getting some useful data, as opposed to simply fire forming and not really getting much in the way of useful results other than the brass.

 

[normmatzen]

gstaylorg,

True, you may not be able to measure any attraction between the magnet and a bullet as the bullet is non-ferrous and not attracted by a magnet.

But, when a bullet cuts through a magnetic field at some velocity, it induces a current in the bullet. This current perturbs the field enough to be detected by the electronics. In addition, the bullet looks like a shorted secondary winding of a transformer made up of the coil (primary winding) and the bullet (secondary winding) so there is an inductive repulsion pushing the bullet up ever so slightly with respect to the coil. The same effect is what makes a power transformer hum. The force between the primary and secondary as well as the squeeze and repulsion of the individual core sheets at a 60 Hz rate makes the hum when the transformer is under load.

 

[Ned Ludd]

I had the bayonet unit turned "on" (active) when doing the measurements. Wasn't looking for a "magnetic" attraction/repulsion per se, but any measurable force exerted on the bullet by the bayonet. A repulsive force induced by the current sufficient to displace the bullet should have been detectable by this method. It wasn't. The only argument I can come up with against that result would be that the balance I used wasn't sensitive enough, although at .00001 g readability, I rather doubt that. Honestly, the specific underlying mechanism isn't so important to me as is simply being aware that the effect does occur. So whether it's caused by muzzle blast, or a current induction effect from the magnetic/electronic nature of the sensor, I know that my groups' POI will be shifted slightly with the bayonet attached.

 

[pdq5oh]

I don't see the problem with developing a load based strictly on accuracy, THEN put on the Magnetospeed to check velocity. Some say it's a waste of ammo and barrel life. I don't care to think of the waste I've endured suffering thru erroneous readings with my Pro Chronos. Factor in the cost of the 1 that got shot and the Magnetospeed seems a bargain. The other day I was testing and got what I felt was reliable info on only 3 of 8 different loads I was testing. Needless to say I hope my Magnetospeed gets here by Fri so I can get velocity numbers on the loads that shot accurately enough to bother chronographing.

 

[rardoin]

PDQ...with that frame of mine I think you will find the MS very helpful. I have had a PACT and a CED M2 and neither could be counted on absolutely...thus I found myself repeating tests. As far as shooting a chronograph...I have not done that yet but I would have intentionally if I did not get a MS first!

The only instance in which my MS missed shots was from incomplete insertion of the connector into the bayonet. I must have 200+ shots without a single misread since. Did I mention ease of setup even during a hot range?

 

[Ned Ludd]

I don't see the problem with developing a load based strictly on accuracy, THEN put on the Magnetospeed to check velocity. Some say it's a waste of ammo and barrel life. I don't care to think of the waste I've endured suffering thru erroneous readings with my Pro Chronos. Factor in the cost of the 1 that got shot and the Magnetospeed seems a bargain. The other day I was testing and got what I felt was reliable info on only 3 of 8 different loads I was testing. Needless to say I hope my Magnetospeed gets here by Fri so I can get velocity numbers on the loads that shot accurately enough to bother chronographing.

It's possible, even sometimes common, to find charge weights that can give reasonable groupings at 100 yd, but may have very poor (large) ES/SD. For LR, it is generally wise to avoid these nodes. Many that reload for LR shooting are initially looking for the charge weight window where they obtain optimal (low) ES/SD. Once the center of the optimal charge weight window has been found, groups can then be tuned using seating depth and setting the tuner, if you have one installed. For this approach, going back at the end to determine velocity won't work; you need to define the charge weight(s) associated with a low ES/SD window before moving on to seating depth and fine tuning for optimal precision. It is for these reasons that some of us that use this particular approach with the MagnetoSpeed shoot velocity determinations and groups separately. Again, not a big deal, IMO.

 

[DeadEyeDick45]

I gotta tell ya, I'm a bit overwhelmed with ES/SD figures; neck tension(s) the cartridge and my own neck; concentricity; seating depth; anneal/not anneal or how far down the case to anneal; weighing of brass, primers, bullets, ect., and any other index of "accurate reloading". I have a rifle that I feel will let me shoot out to 500-600 yards with factory ammo (6.5 Creedmoor) or with my own hand loads. The RPR with Vortex scope and a good set of shooting sticks will take care of 99% of everything I shoot at.
God have mercy on all you BR and LR shooters, you have my sympathy.

 

[hogpatrol]

I gotta tell ya, I'm a bit overwhelmed with ES/SD figures; neck tension(s) the cartridge and my own neck; concentricity; seating depth; anneal/not anneal or how far down the case to anneal; weighing of brass, primers, bullets, ect., and any other index of "accurate reloading". I have a rifle that I feel will let me shoot out to 500-600 yards with factory ammo (6.5 Creedmoor) or with my own hand loads. The RPR with Vortex scope and a good set of shooting sticks will take care of 99% of everything I shoot at.
God have mercy on all you BR and LR shooters, you have my sympathy.

It's very satisfying weighing primers and separating them in to piles of different weights. I do only segregate mine in to increments of .02 of a grain though.

 

[Dos XX]

I have used the MS for several years. I have seen loads that grouped poorly without the MS group great with the MS on the barrel. It basically tuned it. I have seen load that shot tight groups without the MS shoot larger groups with the MS on the barrel. The MS untuned it. I have seen loads that the MS did not change the group size, just the POI.

I have a theory that loads that shoot the same group size with or without the MS on the barrel are really in tune. I have seen this a couple of times but don't have enough instances to call it fact.

All this testing done with .308 and 185gr and 200gr bullets.

 

[rardoin]

I have used the MS for several years. I have seen loads that grouped poorly without the MS group great with the MS on the barrel. It basically tuned it. I have seen load that shot tight groups without the MS shoot larger groups with the MS on the barrel. The MS untuned it. I have seen loads that the MS did not change the group size, just the POI.

I have a theory that loads that shoot the same group size with or without the MS on the barrel are really in tune. I have seen this a couple of times but don't have enough instances to call it fact.

All this testing done with .308 and 185gr and 200gr bullets.

I was testing charge loads yesterday with 5 shots for grouping without the MS and 5 for velocities with the MS attached. On two charges the grouping was significantly better with the bayonet than without and on one the grouping was slightly better (great groups with and without) with about a .5 diagonal POI change. I usually get very little group size change and a 1 inch elevation/.5 inch windage change. This is the first time this has happened. This was while chasing a higher node. I think I have found a nice stable node as the bayonet made almost no difference and the ES was 10, SD 4. Velo verified with only 5 shots but show great promise.

 

[Link]

I think I will add a little info to this very technical post. There is a force ahead of the bullet, when you leave the alignment bar in place with adequate clearance for the bullet it goes forward not backwards.

lol

 

[eric n]

For those of you that experience poi change but no impact of group size, do you experience this through different barrels and calibers? Or more specifically, do you experience no change with a finicky bullet to tune vs a forgiving one? Ex... A .233 run hard with heavies or the 20's vs a 6 br or 308?

 

[6BRinNZ]

For those of you that experience poi change but no impact of group size, do you experience this through different barrels and calibers? Or more specifically, do you experience no change with a finicky bullet to tune vs a forgiving one? Ex... A .233 run hard with heavies or the 20's vs a 6 br or 308?

I can't definitely say my group size isn't affected, but I can say my scores and x count are not affected from 300 - 1000 F-class FTR .308 and FO 6br, completely different barrel profiles setups etc.
In both setups I have to come down 1 moa.
I don't doubt that putting something on the barrel will affect harmonics (so I don't develop loads with it on) but in my application it appears to have a smaller impact than the wind so it is fine to get data from it while competing (club days).

 

[eric n]

QUOTE="6BRinNZ, post: 36790476, member: 1275534"]I can't definitely say my group size isn't affected, but I can say my scores and x count are not affected from 300 - 1000 F-class FTR .308 and FO 6br, completely different barrel profiles setups etc.
In both setups I have to come down 1 moa.
I don't doubt that putting something on the barrel will affect harmonics (so I don't develop loads with it on) but in my application it appears to have a smaller impact than the wind so it is fine to get data from it while competing (club days).[/QUOTE]
Interesting...
Thanks for the reply. Maybe I need to look at what I'm doing a little harder.
I better order a couple of more barrels