Spotting scopes redux

Is mirage or "shimmer" more of a factor with larger magnification -- or is it just more visible? It would seem to me that it is what it is -- uncertainty and variability of an optical ray path -- regardless of the magnification used when noting it.

That said, my humble opinion is similar: 20X would be about right.

I don't see much shimmer at 50 yards, even over water at 50X, but it may be different over hot sand in the desert. I've zero desert experience.

And now a question: "shimmer" is noise, temporal variance due to turbulence. But when it is present, there is also usually a vertical density gradient, which causes "mirage" in the sense of reflection/refraction that makes a hot surface look wet. The average density gradient in the air causes refraction. Does this density gradient also cause "refraction" of the path of a bullet? I would think so, though the degree would very likely not be the same as it is for light, but either greater or lesser, and would also depend strongly on the mass and velocity of the bullet.

Hm. If a bullet is affected by this gradient, would the "shimmer" (noise, temporal variance) cause a wider dispersion at range resulting in larger groups?

Its been in my..my experience..that there is indeed some varience as a result of the same conditions that cause mirage. Which is no more than heated air defracting light differently. The heated air component does indeed impart some outside force on the bullets flight, more noticiable over very long distances. I regularly shoot at 1000 yrds or more with .30 cals and the thermals a bullet may encounter when shooting over a long, nonhomogenious distance can add some complications to ballistics calculation. Plus the air is thinner over the hotter areas. The shimmer you see is no more than that thermal air being moved around a bit by faint breezes caused by its own uneven rises.

I will shoot a tighter 1000 yrd group on a still calm cool day, than I will on a still calm hot day. Plus of course the mirage effect makes it difficult to even place the sights on the target..in some cases..trying to figure out which of the three mirages IS the real target can be interesting

Gunner

Confronting Liberals with the facts of reality is very much akin to clubbing baby seals. It gets boring after a while, but because Liberals are so stupid it is easy work." Steven M. Barry

On Tue, 04 Oct 2005 01:40:52 GMT, with neither quill nor qualm, Gunner Asch quickly quoth:

Are you referring to the heat-glimmer type of mirage, or something else?

(There, I snipped the other 100+ lines of unnecessary post, too.)

Thanx awl -- so it's 18 x min, 24 x max. Deep breath, release slowly, hold, squeeze the trigger - got it. But how do you deal with that pesky heart beat?

Bob Swinney

When the sights go off target..you hold what you have. When the sights go back on target, you sqeeze a little more, and so forth. Pretty soon there will be a bang.

On the other hand..minimal stock contact and sandbags will help minimize heartbeat issues. If the weapon is firmly bagged and heavy enough..heart beat becomes much less of an issue.

Prone, offhand and kneeling..those are what seperates the men from the boys..

3 position or prone shooters seldom consume caffeine before a match, and train to be in good physical shape, with a low resting heartbeat.

Once your rifle/optics are good to go..and you have proper rests..the single biggest issue you will need to address is which ammunition your particular rifle prefers. You will need to buy one box of every kind of 22lr ammo, both cheap and expensive, and shoot 5 shots minimum for group.

This may be of assistance

It may surprise you that a $.99 a box brand may outshoot the $7 a box. Its VERY gun dependant.

My Anshutz 54 shoots Winchester Wildcats (less than a buck on sale) nearly as well as Eley Tenex Gold ($7)

Gunner

Confronting Liberals with the facts of reality is very much akin to clubbing baby seals. It gets boring after a while, but because Liberals are so stupid it is easy work." Steven M. Barry

My .02 worth. Agreed 18-24 power works well at 50 yards. I disagree that mirage is a problem. I used to shoot centerfire bench rest with a 44X scope. The mirage helps you see the wind. Its helpful to be able to read the condition of the atmosphere out there. Wind flags aren't enough. Warren Page explains it very well in his book "The Accurate Rifle" in the chapter named appropriately 'Shooting Through the Swimming Pool'.

I have problems finding the target with these magnifications...

i

I guess Im more used to 115F mirage than perhaps you are.

Gunner, California desert.

Confronting Liberals with the facts of reality is very much akin to clubbing baby seals. It gets boring after a while, but because Liberals are so stupid it is easy work." Steven M. Barry

Thanx for the nice links, Gunner! You are "Right on" re. the flavor of ammo. I'm still trying different stuff for my Kimber .22. Attempting sub-1/4" groups at 50 yards brings out all the variables. As said, I shoot off a Hart rest and rear butt stock leather shotbag. You are sooooo right about minimal stock contact. I shoot "std. benchrest" style with my left hand folded back under the rifle around the rear rest with the stock being pinched between thumb and forefinger for elevation control. Stock contact has been eliminated to the extent I am now needing a lighter trigger than came on the rifle. Pulling off a std.trigger works in opposition to minimal stock contact; pulls you closer to the rifle; emphasizes heartbeat, etc.

Bob Swinney

Try the "pinch" method of trigger pull. Simply put your thumb behind the trigger guard, and your forefinger on the trigger..and pinch. If you are sand bagged/rested...the weapon is self supporting, or may be lightly stablized with the off hand. This works even with rough/creepy two stage military triggers.

My long range bench method, is to solidly bag the forend..then bring my lefthand back under the pistol grip, and by opening or closing my left fist a bit...I can control elevation and windage, while my right hand does the pinch method. I regularly shoot the .22 at 200 yrds, which is good practice for centerfires at longer ranges, wind doping, etc etc.

I generally shoot the 300 Winmag and other high recoil centerfires at

1000yrds, and that requires a normal trigger pull, simply to control the rifle when it recoils..as do most centerfires unless you have a good brake installed. The notible exception is the 6.5x55 Swede, which is quite capable of 600 yrd work this way.

Glad to be of help.

Gunner

Confronting Liberals with the facts of reality is very much akin to clubbing baby seals. It gets boring after a while, but because Liberals are so stupid it is easy work." Steven M. Barry

Hmm. I've never done this. I'll give it a try - as soon as the stupid county gets our range open again!!! It's been closed all summer for renovation.

Their idea of renovation is ripping everything out with buldozers, and then saying 'what do we do now?'

GRRRRR.

Jim