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cryogentically treat a barrel
frisky-maddog
Member Posts: 208 ✭✭
hello
i have heard of people cryogenticly (freezing) treating there barrel to help improve accuracy. does this work or is it a myth? what is it suppose to accomplish and who does it or how is it done? is it expensive?
i had a freind that has passed and he spent alot of money on accuracizing his 10/22 which happens to include that treatment to the barrel. i never got to shoot his rifle but it looked impressive and he had targets that he shot with it at 100 yard that measured .358. all he wanted it for was shooting squirrels. his kids are considering selling it and i plan on purchasing it but just wondered about the process.
thanks
i have heard of people cryogenticly (freezing) treating there barrel to help improve accuracy. does this work or is it a myth? what is it suppose to accomplish and who does it or how is it done? is it expensive?
i had a freind that has passed and he spent alot of money on accuracizing his 10/22 which happens to include that treatment to the barrel. i never got to shoot his rifle but it looked impressive and he had targets that he shot with it at 100 yard that measured .358. all he wanted it for was shooting squirrels. his kids are considering selling it and i plan on purchasing it but just wondered about the process.
thanks
Comments
It is a variation of stress relieving metal that has developed stresses from the manufacturing process. Prior to Cryo treatments, heat was the only method used for stress relief. The metal changes molecularly and the machinability changes (ask me how I know...).
John Krieger still uses the Cryo treatments but he has it done only once now instead of twice.
In a Nutshell: What Cryo Does
"There's a little science here, but it's easy to digest. When tooling is made, the manufacturer heats it to make it hold an edge. During heat treatment, the structure of the steel changes. As it is heated, the steel has a structure that is called "austenite," which is softer and has a coarse, irregular grain. When the blade is quenched (reduced quickly in temperature), the austenite changes into "martensite," which has a finer grain and is more resistant to wear.
The problem is that the transformation from Austentite to martensite is never 100%. If a tool is carefully treat treated, it might end up with 90% martensite and 10% austenite. Commercial heat treating typically results in about 75% martensite, Bryson says. In low-quality tooling, it can be as slow as 50% martensite.
By carefully cooling the tooling to -320degrees F and then thoroughly re-tempering the metal, nearly all of the austenite is transformed into martensite. Bryson says it's proven to be 99.9% transformation or more.
All tooling will benefit from cryogenics, Bryson says. But if the steel is an alloy containing cobalt or tungsten, the cryogenic process will create very vine micro-carbides, which add even more durability to the edge."
You can explore this site as they are one of the very first companies to utilize this process.
http://www.300below.com/
From Dan Lilja, Lilja barrels,Inc.
"Q. What is your opinion of the deep cryogenic processing of barrels?
A. The cryogenic treating of barrels at a temperature of -300 degrees below zero has been a hot topic of discussion lately. Our short answer is that it will not harm your barrel but we are not completely convinced of all of the benefits claimed by some. The only benefits that we feel are likely to result from the treatment are possibly a longer barrel life and a slight increase in machinability.
Claims for increased accuracy through stress relief are not founded in our opinion. When barrels are button rifled no material is removed, it is just displaced. This causes stresses to be formed in the steel. If these stresses are not removed problems will result. These negative conditions include warping of the barrel during other machining operations, an increase in the bore diameter towards the muzzle end of the barrel during the contouring phase, and in the extreme, lengthwise splitting of the barrel. Also, if there are stresses remaining in the barrel they can be slowly released as a barrel warms up during firing. This causes the barrel to actually move during the course of shooting, causing inaccuracy.
In our testing we have found that the only effective means to completely remove the types of stresses introduced during rifling are with conventional heat treating using elevated temperatures. The -300 degree treatment alone will not remove these stresses. We have been told by a knowledgeable metallurgist that the deep cold treatment will, at best, remove up to 6% of the remaining stresses in the type of steel used for rifle barrels. The key words here are remaining stresses. In other words if the barrel was not stress relieved conventionally, then only 6% of the original stress will be removed. If the barrel has been treated conventionally with heat and then brought through the -300 degree cycle, up to 6% of any remaining stresses could be removed by the cold treatment. We do know through our testing that the cold treatment alone will not remove any significant amount of stress and that the problems outlined above concerning stress will remain in the barrel.
So, because of the very limited amount of stress that could be removed with the cold treatment (if the barrel has been properly stress relieved with heat as our barrels are) we do not believe that there can be much if any accuracy benefit to the -300 degree treatment of our barrels. It is for these reasons that we feel the cold process has very little potential for increasing the accuracy of our barrels. In our opinion, other than the removal of these stresses, there are no other mechanical factors involved that could benefit accuracy in a rifle barrel, resulting from a heat treating operation, either hot or cold.
For reasons not completely understood however there may be an increase in the wear resistance of the steel. This type of wear however does not contribute greatly to barrel erosion. We invite you to read our comments on this type of barrel wear in the question regarding the use of moly coated bullets.
Another possible side benefit to the freezing process is a slight increase in its machinability.
Post Script: Since I originally wrote this an excellent article by Kevin Thomas of Sierra Bullets was printed in the September, 1998 issue of Precision Shooting magazine. Mr. Thomas found, in a controlled test, that there was little benefit to deep freezing match grade barrels. He could see no difference in accuracy but probably a slight increase in useful life. I would encourage anyone interested in this subject to take a look at this article."
Best.