Home Forums Hunting & Shooting Gunsmithing barrel stress relief by deep freezing...anyone done this???

Has anyone had this done? Did you notice any real difference? I have a 6MM Ackley. With a cold barrel it shoots 3" to the right. By the sixth or seventh shot the rifle has moved the bullets point of impact 3" left. At this time the rifle settles down and starts to group. The barrel is floated and is a fairly heavy contour with a .800" muzzle diameter. At one time this barrel was chambered as a 22-6MM Ackley. After several prairie dog hunts I had the barrel bored out to 6mm and re rifled. When it was 22-6mm I never experiance the problem with bullets walking as the barrel heated up.

Cyro treating is not used for stress relieving.

I am not sure what the purpose of it is after the part has been put into use for any length of time, after heat treating.

I know that it is used after quenching but before tempering for cold treating knife blades, gears, axels and other items subjected to high stress.

I also do not know if anyone has every proved that it will benefit a gun barrel whenever it is done.

Time for a new barrel!

Had a barrel frozen when I first started having customs built,I really didn't notice much difference!

According to these guy's it is. http://www.nitrofreeze.com/guns.html That was it's original claim to fame for gun barrels. Gun barrels feel like they machine a little smoother afterwards but I haven't been able to detect any accuracy enhancements from having it done. I don't believe it hurts anything.

I've been told, by a very prominent match grade barrel maker, that you cannot stress relieve 416 stainless by Cryo treatment.

Back in the early 90's it was very popular. Outfit called 300 Below, or something like that, was promoting it. I had a 338 Win Mag that was eating telescopes. Both Burris and Leupold, and my gun builder who had coupons for it from 300 Below, suggested harmonics problem and try the stress relieving. My gunsmith had several coupons and I had 3 problem rifles. Sent them all along with someone else's gun. The problem in the 338 was cured. Noticed nothing else different other than a clean barrel came back with lots of very fine carbon, presumably stuff coming out of the pores. In a 308 the accuracy was enhanced tremendously. In a 22-250 there was absolutely no change. The fourth rifle, someone else's, I understand went from a tack driver to 'shotgun' patterns. My rifles 'seemed' to clean easier but that could have been wishful thinking. At that time Krieger was cryogenically treating their barrels in the machining process. They may still do it.

Amen.
I consider it a waste of money to cryo treat any barrel, factory or aftermarket.
The barrel makers know exactly what is required to make some great barrels, and I trust their expertise for what heat treatment is required.
I would never consider cryo treating a perfectly good Hart barrel, or any other well known maker's barrels.
Lastly, I've never read a test report by an independent test activity validating cryo as something required for better accuracy. Independent here means that the test activity has nothing to gain from the test results. Until I do read such a test report, I'll consider cryo treating as snake oil treatment, of no value.
The only people who have touted its merits are those in the cryo treatment business.

Don

I have read quite a bit about cyro quenching. It is not new, it has been around since WW2, and maybe before. It is used to extend the life of High Speed milling cutters and lathe cutters, and other tools designed for cutting steel.

Malm is correct in that it seems to machine easier. I can't say this from experience, but it is something else I have read.

For those you have metelology knowledge, it has to do with the Austinite to Martinsite transformation during quenching.

The problem I have with cyro quenching is the way the ones in the business are doing it.

From all I have read, cyro quenching, to be effective, has to be done immediately during the heat treating cycle. The steel has to be quenched from the heat treating temperture to room temperature, then immediately put into the liquid nitrogen.

Right then, for the martinsite transformation to take place.

Not an hour later, or a day later, or a week, or even several years later, as would be the case for a rifle that has been in use for several years. The cyro quenchers do not do that, however heat treaters who heat treat cutters, tools, knife blades and parts such as axels, bearings, crankshafts and cam shafts and valves, and want the advantages of cyro treating do cyro quench immediately after the steel cools to room temperature. The steel is also cyro quenched before being tempered.

Obviously, if you own a rifle that is several years old, and send it to be cyro quenched, the quenching will not be done immediately after heating it to heat treat temperature, and this is when the benefits of cyro quenching comes into play.

Cyro quenching might have been call stress reliving as a selling point, but stress reliving is not the purpose of it, nor will cyro quenching stress relive. The way a part is stress relieved, from grinding and machining stresses, is that it is put into a furnace and heated to about 1200 degrees F. and soaked at that temperature. That is when it is stress relieved, at least that is how it is done with knife blades and high speed steel cutters.

Then, without letting it cool, it is taken on up to the Austinizing (hardening) temperature, where it is held at that temperature for a given length of time, then quenched, in air, brine, water, oil, depending on the type of steel. This is when the Martinsite formation takes place, and it needs to be done quickly, within a few seconds, or faster, depending on how the steel is quenched. Air cooling would naturally take a little longer to cool to room temperature, but this is when it needs to be done.

If I was offered the choice of a Hart barrel, cyro quenched during the heat treating process, I would prefer it to one that has not been cyro quenched, for the reasons mentioned above.

But cyro quenched a year after it was heat treated, I think would be a waste of time.

I believe that is totally incorrect. The following website has quite a bit on the processes and there is a section referencing gun barrels.

http://www.cryogenicsinternational.com/

"In today's competitive marketplace, the necessity for sophisticated deep cryogenic treating has become a reality. In addition to stress relief, today's companies are finding that controlled deep cryogenic treatment dramatically increases the useful life of components, perishable tooling and wear parts."

Wikepedia also has much more CORRECT information on the subject with no axe to grind and no financial benefit to them.

This is the link to the process for which the principals at 300 Below obtained a US Patent, linked to the patent itself and referencing stress relief.

http://www.google.com/patents?id=4_wWAAAAEBAJ&zoom=4&pg=PA1#v=onepage&q&f=false

I am not aware of any real science (before and after with several replicates) on firearms accuracy or durability and freezing. My readings over the years suggest there are gains with machining and tooling equipment.

Just for grins I did have a Weatherby 30-378 Accumark frozen. It just happens to be one of my most accurate rifles capable of completely hiding 3 rds beneath a dime at 100 yds. Never fired it though before I shipped it off, so I have no idea whether it helped or not.

If someone would fund me to the tune of about a million, I'd be glad to do the science on the accuracy component. My experimental design would be a before and after paired t-test based on 10 shot groups fired from machine rests. I would of course get to retain all arms and equipment.

Durability (barrel life) would be a bit more expensive to study.

Yep. We learned an expensive lesson years ago when making close tolerance parts to be used on oil drilling rigs used in cold climates. The cold temps would cause the martinsite transformation to continue long after the heattreat process was done. Parts would change shape dimensionally causing issues.

From then on parts were cryo'd and ran through a draw oven again...

I talked to Jim Borden about this process and he said he'd done a few barrels to see if it did or didn't make barrels better shooters.He told me he didn't see any significant change in accuracy of the barrels he'd had cryoed.

As I understand it, and I'm no expert, cryogenic treatment helps complete the heat treating process by converting retained austenite to martensite. If everything goes absolutely perfectly you can get 95% transformation to martensite in normal heat treating but that's not a realistic expectation in production. Cryo treating helps make up the difference and so is useful for things like cutting tools. No idea if it makes a meaningful difference for barrels, depends on how well the heat treating went I suppose.

AJ300MAG:

But would the Cyro treating also stress relieve? It is my understanding that the purpose of Cyro treating was never intended to stress relieve.

It is also my understanding that the purpose of cyro treating is exactly what you describe, to change the retained austinite to martinsite.

Also, the parts were stronger, stayed sharp longer, and were more dimensionally stable after cyro treating.

If I understand you correctly, you are saying that the cold would change the dimensions of the part, causing problems, unless the cyro was done immediately following austinizing.

If this is true, a barrel cyro treated later could very well change dimensions, causing more problems that it fixed.

My only experience in cyro treating is sending knifeblades made from 154 CM to a professional heat treatet.

The blades are stress relieved at 1200 degrees F, then taken to austinizing temperature. Then cooled to room temperature and cyro treated before tempering. The stress relieving is done before the knives are even heated to the heat treat temperature.

This person is a professional heat treater, who heat treats the blades of most of the knifemakers nation wide, including many factory blades, and I would trust what he tells me over what I read in Wiki.

Although I was not aware that the martinsite conversion continued after heat treating as you explain in your post, where the parts were put into service in cold temperatures. I thought it happened within a few seconds to a few hours after austinizing.

Conversion of retained austenite will occur over time, slowly of course, at room temperature. They used to age steel for precise gauges. I would suppose that if heat treating leaves a barrel less than homogeneous cryo could make a difference. "Stress" gets used pretty loosely.

I believe the biggest problems with most of the "CRYO" firms is their equipment is not good and minus 300deg is not cold enough. A cryo'd barrel done properly will cut a chamber easier. This talk of martinize, is it like the old dry cleaning firms? Remember the 1hr Martinizing firms? My experience so far has only shown easier machining.
Butch

And who the hell is this Martin guy anyway? Knew an Austen once, a sort of dumb little kid.