I am very interested in getting one of these but was hoping someone could chime in on how using one would affect the results of an OCW test to work up a new load? I understand that the Magneto Speed affects POI but this aspect is a non-issue in my mind. What concerns me is, having the unit clamped onto your barrel and affecting harmonics in your barrel. It would seem to me that this would negate any results obtained while working up your OCW load while using the unit. The answer to this question probably won't affect my final decision to purchase one but from a theoretical standpoint I am quite curious. Once you find your OCW load or even a potential candidate you can always just shoot 10 rounds (or whatever is deemed necessary) to find your critical velocity stats. It would just be nice to see ES & SD while your shooting your OCW so you can use that much more information to make a decision on your final load. Any thoughts?
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OCW with Magneto Speed Chronograph
- Thread starter Bluesop7
- Start date
I ran into this problem recently and decided to change the way I do my load development. Instead of running the chrony throughout the process, I now do the OCW method, determine which charge weight is more tolerant, confirm and then shoot a string of 10 rounds with that load with the chrony to determine the velocity average. I used to be really particular about watching the velocity evolve over the process, but I've had to train myself to ignore it and just focus on pressure signs and which three loads had the most consistent POI. The handiness of the Magnetospeed basically trumps the POI shift, I've come to believe. Of course, your mileage may vary.
Yes buy a magneto. No don't use during OCW. Changing harmonics is changing POI. Furthermore the magneto moves around a bit after each shot, its not a tight fit, being a nylon strap on metal.
My advice, having only shot precision rifle for a year and having been through this the past year: Unless your a 'bench rest'r, do a very basic OCW test at 100 or 200 yds using about 15-20 rounds. Find a good node, load, and shoot. Tweak as necessary and as the throat erodes. Get your velocity after your test. Don't let velocity determine your OCW.
My advice, having only shot precision rifle for a year and having been through this the past year: Unless your a 'bench rest'r, do a very basic OCW test at 100 or 200 yds using about 15-20 rounds. Find a good node, load, and shoot. Tweak as necessary and as the throat erodes. Get your velocity after your test. Don't let velocity determine your OCW.
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I agree. My Magnetospeed changed the POI .4-.5 MILS higher. When I took it off, it went back to original zero.
That's about what I was thinking. I've never used a chronograph before and always had good results with my OCW so I suppose there's no need to complicate the situation and factor in velocity. Kind of defeats the whole purpose of the OCW to factor in velocity.
I'm beginning to wonder if a magneto speed would actually effect the ocw process (other than change the poi) .
Yes I am fully aware that theoretically anything different effects the harmonics. But once again, reality seems to disagree. I have changed brakes on both my 308 and 338 and it did not effect the accuracy of my ocw derived loads. Then just this last week I tested my 308 with my large 338 suppressor and other than different poi, the load performed just as great. It seems like other than all the theoretical talk, others have the same experience as me, or they didn't use ocw to find their load. I guess The point of ocw is to find a large accuracy node, so changes don't effect the accuracy so...
I have no evidence of this, and this is just me suspecting this. Maybe I'll test this out next time I run an ocw and let you guys know.
Yes I am fully aware that theoretically anything different effects the harmonics. But once again, reality seems to disagree. I have changed brakes on both my 308 and 338 and it did not effect the accuracy of my ocw derived loads. Then just this last week I tested my 308 with my large 338 suppressor and other than different poi, the load performed just as great. It seems like other than all the theoretical talk, others have the same experience as me, or they didn't use ocw to find their load. I guess The point of ocw is to find a large accuracy node, so changes don't effect the accuracy so...
I have no evidence of this, and this is just me suspecting this. Maybe I'll test this out next time I run an ocw and let you guys know.
I have done an OCW test using the magneto.... Results were the same on or off. Poi was different but my load selection would have been the same with it on or off....this is using a heavy MTU contour barrel... Having said that, ive come to simply find the OCW then shoot loads with the magneto to get velocity.... Just ended up being simpler..
As said above, the POI changes; and it will change again as/if the strap loosens, you tighten it, or if you detach/re-attach the bayonet. Those facts are easy to verify.
It's up to you whether you think the tool will help, be neutral, or interfere when you pursue OCW, a method that relies on similar POIs of different charge groups to find a node.
It's up to you whether you think the tool will help, be neutral, or interfere when you pursue OCW, a method that relies on similar POIs of different charge groups to find a node.
Two different tools for two different processes. There are velocity/pressure nodes and there are barrel / accuracy nodes.
The chrono is used for finding the velocity / pressure node. You'll notice in your load up that 2 or 3 consecutive charges will give similar velocities. These are your pressure nodes and are vital to producing loads with low ES.
OCW / POI shift is used to find the harmonics that the barrel is happy with.
I have used OCW to make mass-produced loads that shoot great out to 400 or so dispite the SD looking like crap. I've produced loads with ultra-tight ES but accuracy is poor.
When you combine both of your findings you'll certainly have the ONE that works for you.
The chrono is used for finding the velocity / pressure node. You'll notice in your load up that 2 or 3 consecutive charges will give similar velocities. These are your pressure nodes and are vital to producing loads with low ES.
OCW / POI shift is used to find the harmonics that the barrel is happy with.
I have used OCW to make mass-produced loads that shoot great out to 400 or so dispite the SD looking like crap. I've produced loads with ultra-tight ES but accuracy is poor.
When you combine both of your findings you'll certainly have the ONE that works for you.
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I was playing around with using a Gorillapod to mount mine in front of the barrel without actually touching it. It could theoretically work, but it was a pain to make sure it was always aligned properly. During R&D they probably determined that the most consistent and reliable performance came from mounting at the muzzle.
The change in POI is not due to barrel harmonics but due to pressure wave reflections off of the bayonet. This issue could also influence OCW/group size. This phenomenon still exists with a bench mounted sensor.
My preferred chrono is the ones from Kurzzeit, a more traditional setup.
With they're own infrared lightscreen, it's not affected by the normal chronos sensitivity to light and atmospheric conditions.
And they're just as accurate even during nighttime.
Keeping accuracy to 1% on they're economically priced models, it's kind of tough to beat in my book.
No barrel mounting that will affect harmonics etc.
And comes with very good, and fairly user friendly software, where you make a database and keep track of all you're shots, it has 250 shots memory onboard also.ANd a nice infrared remote control where you can adjust all the feautres from.
Reads FPS, MS, ft/lbs and ISPC power factor.
Was looking at Magnetospeed but bought the PVM-21 and could'nt be happier with it.
Still costs about twice of a Magnetospeed, and this is a economically priced unit.
They're top models are certainly nicer with more options but they cost as much as a new AI AW here.
Been really impressed with the product, german engineering at it's best.
With they're own infrared lightscreen, it's not affected by the normal chronos sensitivity to light and atmospheric conditions.
And they're just as accurate even during nighttime.
Keeping accuracy to 1% on they're economically priced models, it's kind of tough to beat in my book.
No barrel mounting that will affect harmonics etc.
And comes with very good, and fairly user friendly software, where you make a database and keep track of all you're shots, it has 250 shots memory onboard also.ANd a nice infrared remote control where you can adjust all the feautres from.
Reads FPS, MS, ft/lbs and ISPC power factor.
Was looking at Magnetospeed but bought the PVM-21 and could'nt be happier with it.
Still costs about twice of a Magnetospeed, and this is a economically priced unit.
They're top models are certainly nicer with more options but they cost as much as a new AI AW here.
Been really impressed with the product, german engineering at it's best.
It's interesting but I noticed on my 260 using the Magneto there was no POI shift, it's awesome. However on both Sakos my POI was high by an entire MOA at 100Y, it's really dependent on the barrel and muzzle break design as well. At least I'm convinced that's what it's due to. I would guess that it's deflection wave mostly vs. oscillation in the barrel.
Certainly not going to argue what works for you. That said the magneto is superior in many ways to a shoot through chrono. I bring my magneto on every shoot as it's so easy to get data on the fly without any real set up. I can get MV data a few minutes before I am going to shoot that specific lot of ammunition.
It's more an ease of use issue for me.
We have shot a number of different rounds within a caliber and separate calibers and have not noticed any repeatable and consistent POI shift at 100 yards.
In .308/7.62 NATO we've shot 147, 155, 168, and 175. In .223/5.56 NATO the two rounds we've shot are 62 and 77. Our normal protocol is the first 10 rounds use the magnetospeed to capture all muzzle velocity and environmentals via Kestral. After that, it is removed for the remainder of our tests for that particular round. When we switch to a different round, we repeat the procedure. We find for us, this procedure works well for both DI and bolt weapons. Additionally, for continuity the chrono is placed at the same location each time. If one is concerned about the quality of the signal generated, the manufacturer provides additional information on a diagnostics page.
Additional Info: Our initial data collection to verify zero is done at 100 yards. The shooter capability is generally +/- 0.1 mil with the weapon the same, giving an overall +/- 0.2 mil variability within each shot. At that point, the ammo and weather determines the group size. FWIW, that is one area I feel some shooters don't fully appreciate - the accuracy of the entire system is not just the shooter and the ammo. Add up the variance btwn shooter, ammo, the weapon itself, and environmentals; and that will give you a much more realistic appraisal of employing that system. By far, the weakest point in the kill chain is the human. Having a very realistic number for the accuracy of any weapon system is part of the command decision on what weapon systems are added to, or subtracted from, a battle area based on ROE and which targets allow collateral damage.
In .308/7.62 NATO we've shot 147, 155, 168, and 175. In .223/5.56 NATO the two rounds we've shot are 62 and 77. Our normal protocol is the first 10 rounds use the magnetospeed to capture all muzzle velocity and environmentals via Kestral. After that, it is removed for the remainder of our tests for that particular round. When we switch to a different round, we repeat the procedure. We find for us, this procedure works well for both DI and bolt weapons. Additionally, for continuity the chrono is placed at the same location each time. If one is concerned about the quality of the signal generated, the manufacturer provides additional information on a diagnostics page.
Additional Info: Our initial data collection to verify zero is done at 100 yards. The shooter capability is generally +/- 0.1 mil with the weapon the same, giving an overall +/- 0.2 mil variability within each shot. At that point, the ammo and weather determines the group size. FWIW, that is one area I feel some shooters don't fully appreciate - the accuracy of the entire system is not just the shooter and the ammo. Add up the variance btwn shooter, ammo, the weapon itself, and environmentals; and that will give you a much more realistic appraisal of employing that system. By far, the weakest point in the kill chain is the human. Having a very realistic number for the accuracy of any weapon system is part of the command decision on what weapon systems are added to, or subtracted from, a battle area based on ROE and which targets allow collateral damage.
If you're telling me you've strapped on a Magnetospeed and have experienced zero POI change, I'll buy your wife a new hat.
I think it depends on the rifle as well, on 2 of the rifles I have used it on , there is no shift, but on another 3 there was , but within 1 moa @ 100yards
This is a really interesting discussion for me since I'm getting ready to run an OCW with my R700 at 100y. I also just got my MagnetoSpeed V2 along with a Kestrel from Frederick at BisonTactical.com in CO (good guy and company!). I think I have a good understanding of the OCW node but the pressure node is something I haven't put much thought into. I think what I'll do is work up a wider range of loads rather than starting at a +/- range from what most of the folks with my configuration are settling on (SMK175, LC, Varget, BR2) and run the V2 for the entire set to see if I find any pressure nodes as well as OCW nodes. Then I'll go back and verify POI with my final setup as I work out seating depth.
It sounds like it's just a POI shift that people are experiencing, not a change in the group size. Am I correct in that assumption?
The best thing about the V2 for me is the fact that you can set it up while the line is hot. Total pain to realize you didn't align it correctly or square it with the target/rifle after the line goes hot and you have to wait around...
It sounds like it's just a POI shift that people are experiencing, not a change in the group size. Am I correct in that assumption?
The best thing about the V2 for me is the fact that you can set it up while the line is hot. Total pain to realize you didn't align it correctly or square it with the target/rifle after the line goes hot and you have to wait around...
The MagnetoSpeed is a great tool, but IMO it isn't friendly with load development. The MagnetoSpeed offers near-zero setup with no need to have the whole range go cold, next to no danger of shooting it, and no worries about light conditions.
But attachment to the barrel causes a POI shift. Importantly, if the strap is tightened or loosened, or the device is mounted slightly further fore or aft on the barrel, the POI will shift again.
Personally, I won't introduce that kind of variability into my load development. YMMV.
Again personally, I find knowing the velocity of the load development rounds I have actually used is a significant benefit to me. YMMV.
So, whenever possible, I use a "standard" chrono during load development . . . my MagnetoSpeed comes out whenever using my CED isn't possible. If my range(s) precluded a standard chrono, then I'd do what has been recommended above, ie, chrono loads after load development, using (obviously) different rounds.
But attachment to the barrel causes a POI shift. Importantly, if the strap is tightened or loosened, or the device is mounted slightly further fore or aft on the barrel, the POI will shift again.
Personally, I won't introduce that kind of variability into my load development. YMMV.
Again personally, I find knowing the velocity of the load development rounds I have actually used is a significant benefit to me. YMMV.
So, whenever possible, I use a "standard" chrono during load development . . . my MagnetoSpeed comes out whenever using my CED isn't possible. If my range(s) precluded a standard chrono, then I'd do what has been recommended above, ie, chrono loads after load development, using (obviously) different rounds.
I had been killing 2 birds with 1 stone--doing OCW w/Magneto attached. I did like all the data. Group sizes were 'probably' unaffected. Multitasking, it seemed.
Lately though, I have been looking at them as 2 distinct operations--find a good OCW node/set with a naked barrel, then grab MV. Goes through several more rounds, but I feel it lends itself to the most unbiased execution of these 2 different tests.
I'm happy with sticking to keeping them apart from here on out.
Lately though, I have been looking at them as 2 distinct operations--find a good OCW node/set with a naked barrel, then grab MV. Goes through several more rounds, but I feel it lends itself to the most unbiased execution of these 2 different tests.
I'm happy with sticking to keeping them apart from here on out.
couple of things I do that may help others when using the MagnetoSpeed..
1. Tighten the strap according to the directions - and use the rubber heat shield (if you have the V2) - the band doesn't slip then
2. I make a couple of index marks on my suppressor with a paint pen - then makes getting the V2 back into almost the exact same spot pretty simple.
I would suggest that the number of variables introduced into a conventional chronograph are likely much higher than when using the MagnetoSpeed...
1. The distance from the first recording sensor on the Magneto speed vs the distance to a conventional chornongraph is likely to be more consistent
2. The distance between the sensors on the magnetospeed vs a conventional chronograph are more likely to be more precise (on the MagnetoSpeed they are embedded and don't move and precisely calculated during assembly).
1. Tighten the strap according to the directions - and use the rubber heat shield (if you have the V2) - the band doesn't slip then
2. I make a couple of index marks on my suppressor with a paint pen - then makes getting the V2 back into almost the exact same spot pretty simple.
I would suggest that the number of variables introduced into a conventional chronograph are likely much higher than when using the MagnetoSpeed...
1. The distance from the first recording sensor on the Magneto speed vs the distance to a conventional chornongraph is likely to be more consistent
2. The distance between the sensors on the magnetospeed vs a conventional chronograph are more likely to be more precise (on the MagnetoSpeed they are embedded and don't move and precisely calculated during assembly).
I called them about this today. They have not done this. They did, however, modify a bayonet for guy who made some bench top gadget. They had to do minor modification and something to do with the wiring for the guy. He said that this gut posted pictures on the net and they have been getting calls about it.
Thanks for the link to the post. Now I see what they did to modify it for him. Looks like the cut off the part that goes on the barrel and eliminated the plug in part on the bayonet. So, they have a free wire running from it. I took it that from the guy that they basically modified the bayonet only and that the rest of the assembly was what the guy rigged up. He did tell me that they may look into developing such product.
Just a few final cautionary notes:
- Every one of our reported experiences is purely anecdotal. IOW - other than concluding that the POI often changes, and can change variably on the same barrel -they are scientific evidence of nothing useful to anyone else.
- I personally haven't seen sufficient data to show that there is an effect on group size and/or shape. My personal "anecdotal" experience with about 25 3-shot groups using the same component composition with and without the MagnetoSpeed attached is only that *MY* average group size is slightly larger with the MS attached. Proves nothing.
- Maybe I missed it, but the manufacturer does not address this seemingly obvious potential issue in their literature or on their web site. That's a warning sign to me.
- Every one of our reported experiences is purely anecdotal. IOW - other than concluding that the POI often changes, and can change variably on the same barrel -they are scientific evidence of nothing useful to anyone else.
- I personally haven't seen sufficient data to show that there is an effect on group size and/or shape. My personal "anecdotal" experience with about 25 3-shot groups using the same component composition with and without the MagnetoSpeed attached is only that *MY* average group size is slightly larger with the MS attached. Proves nothing.
- Maybe I missed it, but the manufacturer does not address this seemingly obvious potential issue in their literature or on their web site. That's a warning sign to me.
My personal experience is that it does NOT affect group size in any way shape or form. In fact my best group size ever out my bone stock 24" 308 5R off a bipod with a triad rear bag and a timney flat blade trigger got me this
All with the magneto attached. Infer what you will but I think its a sweet rig and I have been very happy with it. WIth that said I do load development first then I strap the magneto on to get my dope. Who cares how fast the bullet is going if it isn't printing good groups?
All with the magneto attached. Infer what you will but I think its a sweet rig and I have been very happy with it. WIth that said I do load development first then I strap the magneto on to get my dope. Who cares how fast the bullet is going if it isn't printing good groups?
Actually, they do address it:
https://magnetospeed.desk.com/custo...-g-the-location-and-size-of-my-shot-grouping-
https://magnetospeed.desk.com/custo...-g-the-location-and-size-of-my-shot-grouping-
I did the very same thing. As long as all of your OCW testing is done with the Magnetospeed in place, there is no difference in the results. It will only be a problem if you are mixing it up both with and without it mounted.
I'm sure glad y'all have been discussing this before I went out to shoot a new load in my 300wsm in the next few days. I have a Magnetospeed and I have been contemplating this very discussion, and more or less had come to the conclusion that I was going to shoot the OCW method, then find the load I want to use and chrono it after. Nice to see I was probably going to do the right thing. I did think it would be nice to have MV/SD/ES data for each but I didnt think it seemed all that necessary if what I was looking for was the accuracy node, and as someone mentioned above there are rifles/loads that are very accurate with "large" SD and also loads that have very tight SD that are not accurate.
If components werent as expensive as they have become (and more difficult to obtain) I would entertain the thought of loading more and shooting 2 seperate strings - 5rnds each load MS on and repeat it with MS off (or vice versa). Just to see how "relatively unaffected" it would be - in this rifle at least. It seems there are plenty of people that dont see POI shift - but I am curious to see the accuracy with it on vs. off. I'm just going to have to be content with doing what the general populus seems is prudent - testing MV after finding the accuracy node, then fine tuning.
I do like that table top version too, though. Not just for rifles either....I think with some caution I could be able to tweak my .45 loads as well with that. I'm sure some might cringe at the thought as firing a semi auto pistol behind their MS, but I have some ideas now.
If components werent as expensive as they have become (and more difficult to obtain) I would entertain the thought of loading more and shooting 2 seperate strings - 5rnds each load MS on and repeat it with MS off (or vice versa). Just to see how "relatively unaffected" it would be - in this rifle at least. It seems there are plenty of people that dont see POI shift - but I am curious to see the accuracy with it on vs. off. I'm just going to have to be content with doing what the general populus seems is prudent - testing MV after finding the accuracy node, then fine tuning.
I do like that table top version too, though. Not just for rifles either....I think with some caution I could be able to tweak my .45 loads as well with that. I'm sure some might cringe at the thought as firing a semi auto pistol behind their MS, but I have some ideas now.
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