do we really need a chronograph to tune a barrel?

[searcher]

To reemphasize what Nomad47 stated - es/sd has no correlation with barrel harmonics and a lot of people seem to think the Magnetospeed will not give them accurate readings. I have also noticed that most stating this are NOT Apeople actually using it. The Magnetospeet may change P.O.I. slightly but the point in using it is not to "tune" the rifle, but to determine factors of velocity.

A chrono of any type is absolutely not needed to find a load that works well in your rifle, or even to find the perfect tune. It WILL help tell you if your velocity is low enough to warrant going up the ladder to the next node, in telling you which load may be best on es/sd. Using the actual velocity applied to ballistics tables, will help to better determine how much drop and wind drift you can expect if that is important to you. My chrony works poorly in poor light and when too close to the muzzle. I don't use the shades oftentimes and that can help under certain conditions.

 

[6BRinNZ]

Out of curiosity - for those that don't use a chronograph AND develop at short range for long range multi distance shooting (f-class disciplines as an example) - how do you go about diagnosing your vertical when it occurs at long range?

 

[ebb]

Norm are you saying we have been wasting our time free floating a barrel all these years? Cause any thing that effects barrel harmonics will influence the shot. If it is a constant maybe its all good after you adjust POA to POI. But just like a tuner any thing added will change the harmonics.

 

[6BRinNZ]

Norm are you saying we have been wasting our time free floating a barrel all these years? Cause any thing that effects barrel harmonics will influence the shot. If it is a constant maybe its all good after you adjust POA to POI. But just like a tuner any thing added will change the harmonics.

Norm is just saying that you need to verify. For instance If you are shooting .5 moa would you see a difference in agg on group size?

I don't think there is an arguments about harmonics - the argument is about what is detectable when attaching the magneto. Again the consistency of bullet deflection via the magnetic field or blast may be a larger inconsistency than any harmonic affected.

The one thing that can be said for Norm is he is practically analyzing rather than working from theory alone.

Personally I have developed loads without the magneto and used it out to 900 yards in FO and quite happily held the 10 ring. Not a preferred sequence but was an excellent way to get an accurate load and importantly ES/SD data under match conditions.

 

[Cassidy]

I don't understand how the magnetic field from the MS can slightly deflect the bullet up on the POI, maybe half an inch or less at 100 yds. My understanding is that magnetic fields influence iron/steel, and since most BR bullets are copper/lead, I don't understand how they can be deflected. Do I have the wrong understanding of this magnetic field from MS?

 

[jlow]

I think it is incorrect.

The idea that snakepit put forward in this thread that the shock wave of the bullet as it exits the barrel and hits the air” and encounter the Magnetospeed bayonet and is reflected back on to the bullet makes the most sense.

http://forum.accurateshooter.com/index.php?topic=3850095.15

 

[amlevin]

Before I finished the sighting rounds, the chronograph started reading "err" intermittently, then for every round, so I got no muzzle velocity readings during the tune test

Sounds like you had a lighting problem. I had this occur all the time with my 'shooting chrony'. Problem went away when I purchased a chrono that uses Infra Red Sensors. Because power is a rarity at most ranges I just built a battery pack that holds 4 D-Cells to power the sensors.

I now get nice consistent readings, regardless of where the clouds move or what direction the sun is coming from. Total investment of about $300. No trying to strap on a Magneto Speed or waiting for the Doppler Radar setup. Just a nice dependable Chrono that I often let others use when it's set up.

 

[normmatzen]

Cassidy,

Yes.

Any metal moving through a magnetic field will have current induced in it and feel a force due to this Edy current effect.

What you are confused with is that currents in a ferrous metal act way differently than in a non-ferrous metal like brass. This is a large factor in inductance heating.

 

[Ares]

Norm's theory is not a theory it's simply physics, and he is correct. Have pretty much the same background as for education, and that is quite Basic knowledge.
It is a lot more reliable then some of the theories some People come up with.

If this is a worry for the OP and he wants a reliable chrono of the traditional type, the above mentioned Kurzzeit Pvm-21 is as good as it gets for a overcomeable price, they have also used infrared sensors to remove the effect of lighting conditions from they started making the products

 

[BoydAllen]

When you pass a conductor (bullet) through an electromagnetic field, the voltage that is running through the electromagnet is momentarily reduced by counter emf (voltage running the opposite direction (DC)) If we have a way to "see" this blip. we have a way to start and stop a timing circuit. I believe that this is very likely to be the basic operating principle of the Magnetospeed. In addition to this, in the conductor, eddy currents are created that produce an magnetic field. This is how magnetic damping works in a balance scale. The magnetic force that is produced has the opposite polarity of the permanent magnets in the scale, and is in proportion to the velocity of the copper piece that moves between them, so there is no force on the beam when it is at rest. The question is whether this momentary repulsion between the moving conductor (the bullet) and what is undoubtedly a small magnetic field is enough to significantly deflect a bullet. This could be tested with a simple magnet attached to a fixture so that it is the same distance from the line of the bore. A piece of steel of identical size and weight could be substituted for the magnet so that the weight added to the muzzle would be the same and in the same place. Of course to be precise, there would have to be some way to determine if the magnetic fields of the magnet and the Magnetospeed were of similar strength at the distances that they were from the line of the bore.

 

[Cassidy]

Thanks, Norm, Ares and Boyd for the clarification.

 

[sparky123321]

A chrono is a very useful tool for establishing the velocity of a given round, which allows you to better determine your drop and drift at various distances and conditions. However, if you are experiencing unacceptable variations in your velocity from round to round on a given day, which will have an impact on your accuracy at any distance, you are really looking at and need to fine tune your reloading process not your round to your barrel. Numerous factors during reloading will cause deviations in velocity. Here are just a few, but the list could go on and on.

Inconsistent powder charge - My personal favorite
Inconsistent case volume/case weight/thickness
Inconsistent neck tension/thickness/annealing
Inconsistent bullet weight
Lot to lot variations in brass, bullets, powder and primers
Inconsistent seating depth
Bullet concentricity

This is why most of us accuracy nuts weigh and sort our bullets and brass, turn and anneal case necks, weigh our charges to .01-.02gr and not .1-.2gr., check concentricity and even go as far as weighing our primers. Reloading is really a science. The more consistent you and your components are the more consistent your velocities will be.

All that said, I do not personally use my chrono when working up a round for a new rifle or barrel and I would never hang a MagnetoSpeed or anything else off my barrel while doing so. I would have no problem using a MagnetoSpeed to determine average velocity or ES though.

 

[Cassidy]

Sparky - havn't heard the "weigh the primers" approach before. How much does variation in primer weights have on group size?

 

[sparky123321]

I haven't tried weighing them yet myself. Just a little trick I read about recently. Makes sense though. Inconsistent ignition of the powder due to the strength of the primer charge could definitely be a factor as would inconsistent primer holes. We're really splitting hairs at this point, but it all matters and adds up when going for extreme accuracy and repeatability.

 

[jlow]

The other question that needs to be asked first is which force is more significant?

In my mind, the blast that accompanies the firing of a rifle bullet is very significant. Any one who has fired a compensated rifle next to a barricade and seen the material that makes up the barricade get blown apart knows the forces involved. Now a non-compensated rifle will not direct this force to quite the same extend but it is not hard to see that it is likely of a different magnitude than the meager magnetic force being discussed here.

 

[Cassidy]

Maybe differences between primer brands is really a difference in variance of the primer charge within each brand.

 

[BoydAllen]

Wrong!

 

[savagedasher]

A chrono is a very useful tool for establishing the velocity of a given round, which allows you to better determine your drop and drift at various distances and conditions. However, if you are experiencing unacceptable variations in your velocity from round to round on a given day, which will have an impact on your accuracy at any distance, you are really looking at and need to fine tune your reloading process not your round to your barrel. Numerous factors during reloading will cause deviations in velocity. Here are just a few, but the list could go on and on.

Inconsistent powder charge - My personal favorite
Inconsistent case volume/case weight/thickness
Inconsistent neck tension/thickness/annealing
Inconsistent bullet weight
Lot to lot variations in brass, bullets, powder and primers
Inconsistent seating depth
Bullet concentricity

This is why most of us accuracy nuts weigh and sort our bullets and brass, turn and anneal case necks, weigh our charges to .01-.02gr and not .1-.2gr., check concentricity and even go as far as weighing our primers. Reloading is really a science. The more consistent you and your components are the more consistent your velocities will be.

All that said, I do not personally use my chrono when working up a round for a new rifle or barrel and I would never hang a MagnetoSpeed or anything else off my barrel while doing so. I would have no problem using a MagnetoSpeed to determine average velocity or ES though.

+++++ Many others. How many times have you had Low ES loads not shoot. I feel your not tuning the barrel your tuning the system. Starting with the Shooter. No matter what ES or how good your load is A Inconsistent Shooter will be the main factor.
I'm heading to friends house to help him with a new Rest. Will the same load & system shoot the same . No.
Till we Find where the stop on the front rest must be and the rear bag location and firmness of the rear bag the gun will never Repeat. ES is only one part of many in a System. This is why I think Tuners work. Larry

 

[Webster]

I had a barrel with a tuner on it. I could change the size of the groups with the slightest turn of the tuner ring. No way I would hang something on my barrel that can move around. I like to shoot groups at the distance I want to compete. I have shot great groups with bad ES and I have shot bad groups with good ES.

Would you say bullet stability is not related to ES and SD?

 

[Alex Wheeler]

Would you say bullet stability is not related to ES and SD?

Yes