Does Mirage shield affect harmonics?

[jrm850]

I was load testing this morning and started getting a little mirage as the barrel was warming up. I installed the mirage shield on my third group which had the lowest extreme spread but the largest group. Just a coincidence or has anyone else noticed changes while wearing a shield?

 

[BoydAllen]

I have not noticed that it has, but the real way to test this is to shoot the same load with and without. What you may have there is a good argument for a tuner. Take your lowest ES load, and adjust the tuner so that it shoots smaller groups. I purposely use home made mirage shields that are light and somewhat floppy.

 

[eric32]

Couple of questions to stir up some conversation on this topic.

How is the mirage shield attached?

What is the weight of shield?

I am leaning more towards you might have a heavy mirage shield that is resting directly on the barrel maybe some sort of buffer between the two might solve your issue.

 

[lawrence97]

Mirage shields are usually very light and I do not think they would affect grouping. Low ES doesn't always coincide with small groups either. My mirage shields are just leftover blinds that I cut and attach with Velcro. Like Boyd mentioned, you may want to look into a tuner or more importantly adjust seating depth to shrink your group. Or stick to what prints small on paper because small groups don't lie! Definitely Worry about ES and SD for long range.

 

[Lbart]

For F-Class I use a rather long and wide shield attached by Velcro. But I always use it. That way I don't have to worry about changes. i believe in the KISS principle.
Larry Bartholome

 

[jrm850]

I have not noticed that it has, but the real way to test this is to shoot the same load with and without. What you may have there is a good argument for a tuner. Take your lowest ES load, and adjust the tuner so that it shoots smaller groups. I purposely use home made mirage shields that are light and somewhat floppy.

It's getting harder and harder for me to ignore that tuners are almost a requirement now if for no other reason than to save a lot of wear and tear on barrels. I would love to be able to pick a low es at a velocity I like and start twisting than have to settle on the hand your barrel dealt you. Do you have a recommendation for which one to use?
I'm definitely going to include that load when I start working on seating depth.

Couple of questions to stir up some conversation on this topic.

How is the mirage shield attached?

What is the weight of shield?

I am leaning more towards you might have a heavy mirage shield that is resting directly on the barrel maybe some sort of buffer between the two might solve your issue.

I made the mirage shield myself out of white .032" thick x 2" wide PVC. I attached it with three 1" pads of Velcro so it is isolated from the barrel somewhat.

I don't have a weight for it, but it is definitely heavier than the aluminum blinds. I would love to use the blind slats but I can only find them about 1" wide around here.

 

[BoydAllen]

On the tuner, there are several. I would get a hold of Erik Cortina, and look around on this site for pictures. I would also look at Gene Buckys' design. It has done well in short range BR. There are others, Gene Beggs, Ralph Stewart, Shadetree Engineering and Accuracy. There are probably others that I left out.

 

[artbosco]

I was load testing this morning and started getting a little mirage as the barrel was warming up. I installed the mirage shield on my third group which had the lowest extreme spread but the largest group. Just a coincidence or has anyone else noticed changes while wearing a shield?

None whatsoever.

 

[LHSmith]

For F-Class I use a rather long and wide shield attached by Velcro. But I always use it. That way I don't have to worry about changes. i believe in the KISS principle.
Larry Bartholome

^^^^^ Yup, always seek to eliminate as many variables as possible. There is no reason to shoot without the shield.

 

[jnyfeler]

I would love to use the blind slats but I can only find them about 1" wide around here.

Sinclair sells them. http://www.sinclairintl.com/shooting-accessories/benchrest-equipment/sinclair-barrel-mirage-shade-prod32718.aspx

Jeff

 

[Uthink Uknow]

Every and any thing you do has something to do with harmonics. Some mirage shields have more effect than others. Some guys use the "Venetian blind" attached via Velcro and these have some effect. Some merely tape a piece of old target "with a tiny group" taped to the bottom of the scope and the top of the barrel. I feel these have less affect from my experience. I always have the venetian blind/ Velcro attachment all the time. I tune with a Gene Beggs tuner and that has been a winning combination for me.

 

[Erik Cortina]

I believe barrel harmonics behave similar to powder charge and seating depth. If you are on the ragged edge of the node, very small changes will have huge effects on accuracy.

Test with shade on and off with same powder charge and verify.

 

[butchlambert]

We are out of the tuner business(Shadetree Engineering). Mike Ezell makes a great tuner.