Do Harmonics affect Velocity?

[RyanTrials]

Thinking about getting a Magnetospeed chrono.

I understand that changing the harmonics of the barrel can affect POI shift and possibly group size on some barrels..

But what about velocity? Lets say I shoot 10 identical rounds with the magnetospeed on the barrel. Then shoot the same identical 10 rounds without the magneto, is there a possibility of having a magnetospeed actually change the average muzzle velocity?

The people that develop loads and use a magnetospeed generally only use it after their ladder/load workups, just to check velocity/es/sd. That makes sense, but what if when you take the magnetospeed off and go out for hunting without it on, what if your velocity is then different? Has anyone tested velocities over an oehler with a magnetospeed on and off with identical loads?

Hope you understand what im getting at.

 

[Pdvdh]

I say no, as I can't imagine how or why. But I don't own the magnetospeed and have never tested for a velocity shift.

 

[dok7mm]

I see what you're asking. When I used the MagnetoSpeed, I never noted a change of speed affecting POI at targets shot without it, although using it will often change POI somewhat. I don't think actual fps would vary, outside of normal established ED. Just last week, I shot 5 rounds with MagnetoSpeed attached and monitered it with my LabRadar. The MS showed a consistent 6 fps higher velocity than the LR. That difference was probably due to where each unit was picking up the bullet or even calibration of the units. I really doubt you could notice the difference, unless you shoot your drops at long distance, with and without the MagnetoSpeed and measure the difference of vertical. Don't worry about it --- you'll need to true your drops, for speed or BC, anyway.

 

[RyanTrials]

I was just thinking, when you encounter low es/sd loads for long range, arent those low ES loads reliant on certain barrel harmonics? If so, finding a good low SD load with the magneto would be a waste, unless you leave it on your rifle always...

Im not happy with my caldwell BP chrono, and the whole reason I want to upgrade it is to find a load with the best balance of precision while also having the lowest ES possible. In testing currently ive found very precise groups and very low ES loads, but theyve never coincided with each other unfortunately

 

[RockyMtnMT]

I was just thinking, when you encounter low es/sd loads for long range, arent those low ES loads reliant on certain barrel harmonics? If so, finding a good low SD load with the magneto would be a waste, unless you leave it on your rifle always...

Im not happy with my caldwell BP chrono, and the whole reason I want to upgrade it is to find a load with the best balance of precision while also having the lowest ES possible. In testing currently ive found very precise groups and very low ES loads, but theyve never coincided with each other unfortunately

We use the MS now all the time. We develop with it then remove it for range testing. If there is any change to the load during range testing then we will shoot it over the MS again to confirm vel. Using it makes you do your vel testing separate from range work but we have found that we shoot far less shots this way than we did with a sky screen system. Vel data is now much more accurate and takes out the doubts.

As far as ES goes it is very easy to get carried away with focusing on it. It is not always the best indicator of accuracy. Don't get me wrong, I like to see it as low as possible. It is pretty tough to shoot the difference between a 10fps ES and a 30fps ES. I won't throw out a 30fps ES load just based on that. It does not surprise me at all that your lowest ES loads are not your best accuracy loads.

For me the MS gives more reliable data than anything else that I have used and takes away one of the variables when figuring out long range drops. I no longer make vel changes in my dope to get things to line up. I will adjust bc until I get drops to match up as close as I can to field data. Then you only have to worry about dialing consistency in the scope and sliding bc's depending on the vel of the bullet. They all vary as the vel changes and it is just a matter of finding the one that hits most consistently with your field data. Same bullet in different rigs will often give different field data.

My recommendation is to run the MS and don't look back.

Steve

 

[RyanTrials]

Thanks for the words of wisdom guys, greatly appreciated!