Magnetospeed and Harmonics

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by MMERSS, Mar 22, 2015.

  1. MMERSS

    MMERSS Well-Known Member

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    There were some interesting observations today with the Magnetospeed and harmonics. A tall target test was the intent to check tracking of a newly installed ATACR on a TRG-42. A Magnetospeed was attached for MV verification a fraction of an inch in front of the muzzle brake. After a few shots and a solid zero the Magnetospeed was moved another inch away from the muzzle brake. Another shot was taken to verify the zero. This shot was approximately 1” high. MV was not out of the norm. Two additional shots were taken showing a less than .25” group. Moving the Magnetospeed one inch caused a difference in harmonics to produce a 1MOA difference in grouping. The Magnetospeed was removed and the following group was just over 1.5 MOA low. I would not have guessed this one.

    The tall target test was conducted without the Magnetospeed. ATACR tracking shot groups produced a vertical spread of 31.5” with 30MOA dialed. I enjoy the benefits of the Magnetospeed. IMO, final load development is best suited without the chronograph attached to the barrel with potentially MOA plus change in POI to POA with little displacement or complete removal of the chronograph.
     
  2. FearNoWind

    FearNoWind Well-Known Member

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    Excellent advice. It's only a chronograph and it should not be left on the rifle for group on target load development data. Anything attached to the barrel will alter barrel harmonics - even the muzzle brake.
     
  3. cowboy

    cowboy Well-Known Member

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    MMERSS: I have found very similar results with my magnetospeed 2.

    I have seen more drastic change of impact depending on different barrels and calibers.

    I have a 30-06, .550" dia at muzzle, 22" long barrel that shows drastic impact change with the magneto attached. If you move the magnetospeed, say 1/2", farther away or closer to the barrel you really see the impact difference.

    I sure don't miss having to deal with light sensitive type chronies anymore but I will never use my magnetospeed for any purpose other than to gather data.
     
  4. MMERSS

    MMERSS Well-Known Member

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    Load development with the TRG was conducted with an Oehler the previous year. The intent of the Magnetospeed was to reestablish SD and MVV (ES) considering the rifle sat in a gun cabinet for half a year. The chronograph worked well for this purpose…..only gathering data and not used during load development, zero, calibration, or validation.

    Not using this type of chronograph on any rifle barrel may be well better served with a possible POI shift of 2.75 MOA (could be more) as seen on this rifle. One could end in constant tail chasing not realizing the harmonic difference with even the slightest change in chronograph placement.



     
  5. phorwath

    phorwath Well-Known Member

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    That's why I never considered buying one, initially. One company making this sort of device asked me if I'd try one of their proto-type units, and compare the data to my triplicate chronograph setup. I wasn't interested when I heard the unit had to be strapped to the end of my barrel.

    Hard to beat for convenience though. I've had some temptation since then, but I still take the time to set up my light sensing chronographs.

    There's a recent Thread on the Forum where a member fastened his Magnetospeed to a rail mounted off his rifle stock. Now that type of mounting system is something that would cause me to purchase a MagnetoSpeed, provided the unit still functioned properly. It would, however, require some thought, ingenuity, and effort to mount the rail from the rifle stock.
    Here's the link to that Thread: http://www.longrangehunting.com/forums/f28/magnetospeed-v3-load-development-151239/

    [​IMG]
     
  6. santee116

    santee116 Well-Known Member

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    I usually incorporate two extra rounds to my normal three round OCW when load testing, just to get an idea of MV and Max pressure with the Magneto V3.

    For example:

    I will load 5 rounds at 41.0, 41.5, 42.0, 42.5, 43.0 etc...

    I will fire the first 2 rounds with the Magneto V3 attached to get a "general idea" of the MV while also working up to max pressure in my rifle for the chosen components. Grouping and/or POI are not a concern in this round of testing, just Max pressure.

    I then proceed with the regular 3 round OCW, without the chrono.

    After I complete the load development, I then shoot 20 or more rounds of the final charge to get a better MV average.
     
  7. MMERSS

    MMERSS Well-Known Member

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    Quite a few seem to follow the same principles with use.

    The primary reason I purchased the Magnetospeed was for temperature regression results. On a cold day a few rounds and the rifle can be set outside for a period of time to allow for ambient temperature to set in. Powder temperature (outside air temperature) can be recorded and a shot taken with the chronograph attached. The barrel can rest for 15 minutes or so with the process completed again. Average MV with powder temperature results are recorded.

    During the cold temperature process additional rounds are placed on the floor of the vehicle with the heater running. After the last cold temperature shot with MV established and while the barrel is still warm, a round from under the heater is shot with MV recorded. While the barrel is still warm the remaining rounds are removed one by one and shot to record the MV. A Kestrel is placed with the ammo on the floorboard to record the powder temperature. MV temperature regression can be established with this method and the Magnetospeed works great for this purpose. An average MV can now be applied to ballistics solvers corresponding to the powder temperature.

    When temperatures warm up the same can be conducted…..I just find it easier to verify potential regression results during one shooting occasion and not wait for half a year….but that’s just me.


     
  8. waspocrew

    waspocrew Well-Known Member

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    I'll hopefully be purchasing the magnetospeed in the near future... I've never considered using it while shooting groups. Once I find an accurate load, I like to get an idea of the muzzle velocity. I'd definitely be strapping in on just to get the MV, not groups.
     
  9. MudRunner2005

    MudRunner2005 Well-Known Member

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    This is how I've been doing with mine, since I got it early last year. I develop a load for the rifle, then I put on the chrono to find my average velocity out of 10 shots.
     
  10. lamiglas

    lamiglas Well-Known Member

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    Yesterday while shooting two canyon rifle 338 edges and and a sendero contoured 260 we put the magneto on to check ES and velocity. These are loads that we already developed. it was interesting that the 260 shot exactly 3/4 moa higher, perfect windage with magneto installed but still shot really well. The 338's Both shot to exactly the same poi with or without magneto.
     
  11. Cuz

    Cuz Well-Known Member

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    I shoot the magneto speed to verify mv, but I also use a suppressor that weighs about 25 oz. it will change the point of impact, but not the group size. Same with the magneto speed.
     
  12. bigngreen

    bigngreen Well-Known Member

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    I'll develop loads with the Magnetospeed on the barrel, I've seen a few move the POI but I have not see a change in groups size with the Magnetospeed. I'd rather risk the magneto causing an issue than to do total load development without solid velocity data.
     
  13. azsugarbear

    azsugarbear Well-Known Member

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    I have never used my Magnetospeed during the load development stage. When shooting ladders and groups, nothing but the bare barrel is used - just like it would be when hunting. There are only a couple of times when I use the magnetospeed: 1) when I think I have found a load/group and want to check my es; 2) after my final load is selected to give me an idea where to start in terms on muzzle velocity while developing a rough drop table.

    I have noticed the the POI changes more on thinner barrels than bull barrels. That was one of my ahah! moments. I was using it on a new load for my 6.5-06 AI. I wanted to get an idea of velocity. I got what I wanted to know in terms of data, but a nice surprise surfaced when I went to retrieve the target. Although my POI had shifted, my group had tightened up from .75 to .50 MOA. I shot several more groups with and without the Magnetospeed just to make sure. Now all of my rifles wear a Limbsaver deresonator.
     
  14. elkaholic

    elkaholic Well-Known Member

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    I usually have a small shift in poi with the magspeed but group size remains quite consistent. One thing to watch is that even when strapped on quite tightly, the recoil can slide the bayo on the barrel. This will usually cause vertical stringing. Another reason not to use it for grouping......Rich