mirage shields

[allen529]

I was looking at the story on accurateshooter bulletin and was wondering has anyone built heat-sinks similar to those found on computer CPU's? Seems to me that would be a way to lower the barrel temp and solve the barrel mirage problem at the same time.

I am sure some of you engineer/machinist could come up with a design that does both without being totally outlandish and obstructing.

Allen

 

[JJH]

A guy I used to work with shot p-dogs quite often and devised the following system. Him and his buddy wrapped copper tube into a coil that was free standing. This coil slipped over the barrel with about 1/4' all the way around the actual only touching upon recoil. The tube was plumbed to a cooler with ice and water and an aquarium pickup/return pump. He claimed it worked well to keep barrel temp and mirage down, but I have only seen pics never tried it myself. Just an idea?

 

[allen529]

LOL gunnut606.

Actually what I am talking about is the finned 'dry' versions not a liquid exchange unit. As it will have to be figured into the weight of the rifle.

Something that will allow the air to circulate over while spreading the heat and allow the movement of air to cool the barrel faster. Similar to fluting but nothing is changed on the barrel.

Allen

 

[BoydAllen]

Mirage shields are lightweight, simple, low maintenance, cheap, and available.....oh and they are used quite successfully by some of the most accurate shooters in the world. You think that you can improve on this? As to barrel cooling, some very successful shooters keep a wet towel in an ice chest and throw it over the barrel to cool it, simple and effective. Why make things harder than they have to be? Go to any range you want, anyone you see with a mirage shield is likely a competition shooter. Worthless news stand magazines, and the need to conform keep shooters from taking advantage of many things that they can afford and which would improve their performance. Consider the effort that people put into evaluating loads with nothing in front of them to see what the wind is doing downrange. On the other hand,it's their hobby.

 

[allen529]

BoydAllen,

Most things in life can be improved upon in one way or another. I was asking a question not stating that I had done something. I am not trying to rain on anyones parade here but this is the advanced gunsmithing and engineering forum. I was putting an idea out and seeing if anyone could contribute something to it.

Most computer heatsinks are small metal pads with fins attached directly to the heatsource using sometype of thermal grease and or screws.

Now why can't someone come up with something new here and not get slapped around for it because its a hobby?

Oh btw the fins would negate the need for a heat shield most likely as more heat would be transfered quickly pulling it away from the barrel especially if place on the first few inches of the top of the barrel and underneath the portion of the barrel in front of the stock. And best of all its dry all the time.

In case you don't know what a heat sink looks like I attached a pic.

Allen

 

[Bob3700]

Allen,

The heat sink idea while a good one for carrying away heat does have a couple of issues.

First, it would alter the harmonics of the bbl. Now you might be able to use it to 'Tune' the harmonics and improve accuracy.

As the fins of the heat sink absorb the heat from the bbl, they will radiate that heat to the surrounding atmosphere and the heat waves will rise and cause problems that it was designed to solve.

You need to get the heat waves away from your line of sight above the bbl.

The extra weight in front of the action would also be a negative as the rifle becomes muzzle heavy. Not a thing conducive to accuracy.

So while the concept is a good one, execution would be the problem as it would not solve the problem it was designed for.

Mirage shields are a pretty simple items that are hard to improve on.

Now, how about a light wt. water cooled jacket that controls the bbls temp.

Keep thinking as you may discover something as elegant as the mirage shield.

Bob

 

[LHSmith]

Actually in short range Benchrest it is commonplace to fire a shot or two off to the side of the sighter mothball,bullseye) in order to heat up the barrel as more often that not the shot from a cold barrel will go out of group. This is done each trip to the line.
I don't know how you can improve,practicality-wise) on the existing mirage shields, not the tube type) and the cold towel....used judiciously of course.
Look at what the military uses,they have got to have researched this ad-nausium.

 

[BoydAllen]

allen529,
Rereading my post, I did come off more than a tad grumpy. Let me revisit the subject in a more considerate manner. There are several problems inherent with your Idea. Bob3700 outlined a few of them. In the world of 1-200 yd. Benchrest, where scopes start off at 36X and go up, mirage is probably more apparent than in other areas of shooting where scopes of lower power are more common.,Even at 24X there is significantly less visible mirage.) The mirage shield does a good job in that venue, and would help many outside of that sport to have a better view of their targets. As to your heat sink idea, I have seen one that utilizes a unit that was designed to cool a CPU including the fan. Unfortunately, for such a unit to eliminate barrel mirage,as viewed through the scope, it would have to sit behind the front of the objective, where there is little room, and somehow prevent the barrel from heating in front of the objective, a difficult prospect, given that very hot combustion gasses traverse the entire length of the barrel, and significant combustion takes place in front of the scope. I encourage your efforts at coming up with solutions based on out of the box thinking. Thomas Edison once said that invention is 1% inspiration and 99% perspiration. Carry on.

 

[dreever]

I've tried various things over the years for barrel cooling and once used a 'shoe shine box' which housed a 12 volt drivers school bus fan connected to a rechargable 12 volt motorcycle battery. Woked pretty well.
A friend devised a copper tube which was inserted thru the bore and connected on both ends with rubber hose going to an small fountain pump in a cooler which pumped cooling water thru the barrel.
Neither of the system's were ideal but did work. Then again it's just more crap to haul along.

Danny

 

[allen529]

Harmonics are definitely a consideration and it might take some fine tuning to get it right.

I am wondering if this is done right could it eliminate the mirage shield and frozen towel routine all together.

I agree the mirage shield is easy and a tried and true method. Guess what I use one too. lol I am looking for a way to remove as much heat away from the bore quickly and a heatsink does it withouta lot of fuss.

Attached is an idea which is not to scale but a free hand drawing so forgive the mspaint skills.

Boyd, no problems mate, I re-read everything again this morning and I may have been a tad over sensitive too.

 

[LHSmith]

Three problems with your design:

#1/ Stainless or CM steel is a rather poor conductor of heat....with your design, the lower half of the barrel will be at a different temp than the upper half,provided the heat-sink is of sufficient size ..capacity... to even work in the first place)..I can't see how this won't change the size/shape of the bore along it's entire length and won't affect accuracy.
#2/ You're cooling efficiency is at the mercy of ambient air temperature, not so great in tropical temps, maybe too efficient in cold temps....so the application would have a limited usefulness.
#3/How would one go about protecting the copper heat exchangers?

It may work with limited success, but I want my shots to hit where I aim, and think accuracy with such a system would be less than the methods I currently use.

 

[queen_stick]

This thread reminded me of a barrel that Volquartsen makes for the 10/22. The barrel looks like a heat sink, and works like one too, but probably not nearly as efficient. I don't know that I would want something like this for accuracy, because of reason #1 that LHSMITH posted.,I could see 'heat rings' in the bore, where each ridge is on the outside fo the barrel?)

https://www.volquartsen.com/pictures/86-radial-fluted-w-mcmillan-th.jpg?h=300&w=800


The design on the Volquartsen barrel is not the same type of theory you're thinking of though... A 'normal' barrel, and a heat sink that attaches. As far as that goes... I like the idea, but I have to agree with LHSMITH on each of his points, especially the inconsistent heat from side of the barrel to the other.

I'm not saying that you're wasting your time. When you prove all of us wrong when you get this thing to work, we'll all be wondering why we questioned your ideas!

Walt

 

[allen529]

LH,

You're such a party pooper. LOL

Yea I kinda thought along some of those same lines with the heat transfer being conducted away from the barrel steel rates not being the same as copper, brass or some other high efficient metal.

My design needs some work to 'work'. But hey I am out of town and needed something to brainstorm instead of writing another damn report. lol

I have heard but not researched that some European barrels are cut with flutes that resemble fins perpendicular to,across) the barrel instead of parallel on the barrel as most are cut here in the U.S.

Oh well back to the drawing board.

Allen

 

[BoydAllen]

If you want a barrel that cools at the maximum rate, this, with the addition of a rough sand blasted finish should do the job.
http://www.lothar-walther.com/396.php

 

[allen529]

Boyd,

That's it we're not friends anymore :nono:! You found the answer to my question albeit in a different form. Well done!

I knew my drawing was poor and was trying to comeup with another in a way that allowed me to show just what those guys do.

I was thinking along those very same lines with a smaller inner diameter blank fitted with a sleeve of copper or brass as its a decent conductor of heat.

Allen

 

[queen_stick]

Allen529... I think you're on to something! Boyd's link to the L-W page hits the nail on the head. If you make your sleeve with fins that run parallel to the bore, you have yourself a heat sink that works on the entire bore,no perpendicular ridges to the bore, or a heat sink on the top or bottom only).

This first part of your idea may be taken care of with this type of design,heat dissipation). Now to integrate something that would deflect mirage from the line of sight?

 

[LHSmith]

Re: L-W rapid-cooling design.
You end up with an extremely thin,ala Weatherby) pencil type barrel ...which leaves alot to be desired in the accuracy department...which to me is what it's all about.
They claim the resulting barrel 'assembly' becomes 'one' although the assembly is not epoxied or soldered together.... I would be skeptical that this design solves the accuracy deficiency of thin barrels from repeated shots.
In addition the chamber/ throat area remains basically unchanged from that of a standard barrel, here again you will change the bore size/ shape at the transition.

 

[allen529]

LH,

I am not so sure. Mike Rock turns his barrels down for carbon fiber wrapped barrels which would not transfer heat. These barrels are supposed to be very accurate. Now just imagine if instead of keeping the heat they were using a heat transfer tape wrap around the barrel which would further enhance transfer away from the chamber/throat area via tape and heat sink metal.

Of course it goes against my original idea of not using a mirage shield because even in tropical conditions the ambiant air with almost any wind would be cooler than a gun barrel shot during a match. Which would result in mirage.

Allen

 

[LHSmith]

You are referring to Advanced Barrel Systems Inc, who use ultra thin barrel blanks from a number of barrel makers, then wrap carbon fiber with a special helix which supposedly is not heat sensitive which theoretically translates into a more uniform tensioned barrel assembly.
You mentioned these to be very accurate.
ABS guarantees sub- MOA.,of which I'm not impressed)
I haven't noticed any on the BR circuit which might mean they just ain't ready for prime time.
Remington has had a CF with a composite barrel for several years, and they ain't selling anywhere near the volume of a Savage Varminter with a good old fashioned steel barrel.

Their market seems to be directed at the AR-15 semi-auto crowd....maybe it has desirable benefits there.... but I for one would not take a rifle to the PD fields that only had 1 MOA accuracy.