Cryo treating a barrel is primarially a stress relieving mechanism. A few years ago the popularity of longer range shooting was just begining to rise and so more people were looking for better toys to play with. Also with the economy doing so well, more folks had more $ to spend and were glad to do it on what appeared as a better product. This tended to get the notice of those companies that were seeing a drop in sales of "off the shelf" guns and a rise in the custom guns. Thus the popularity of it a few years ago.
Does it work. Yes. If a piece of steel has been machined it will have residule stress in it. Conventional heat treating took most of it out or you would never get a good group. You POI would move as the barrel heated up. Enter Cryo treatment. It relieved more of the stress and gave you a more stable product.
Is it the only way to stress relieve a barrrel? No. you can double or triple temper the steel. Each reduces the stress and converts more of the austinite to martinsite than the previous. That is why some of the better barrel makers do it right and see no benifit from cryo treament. Factory barrels probably would be a good canidate for cryo treatment, especially if you notice your POI moving as it heats up.
Read Dan Lilja's article at his web site.
"When working with the public, there are two things you need to remember. - 1. The public is a bunch of ignorant morons. - 2. YOU and I are one of them!"
Will someone please explain to me the mechanism -- the process -- by which cryo treatment relieves stresses in a barrel? Yes, I've read Dan Lilja's website, and his consulting metallurgist doesn't think it relieves any more than 6% of the "remaining" stresses. I'm an engineer with a significant metallurgy background, so would someone please expain how cryo treatment relieves stresses? Low tempertures prevent dislocations from moving, which are required to relieve stresses. So what does it?
I believe the process involves 300 degrees above as well as the 300 degrees below.
I think Krieger used to cryo all their bbls. I don't know if they still do this or not. I have several rifles with Krieger bbls and no matter how hot you get them POI doesn't change. You might email them and ask your question. www.kriegerbarrels.comwww.cryogenicsociety.org is another site that could possibily give insite to what is actually happening to the metal. Let us know.
<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Due to patent litigation we do not cryo treat any barrels/steel once production has begun.
Thanks for your inquiry,
Krieger Barrels, Inc.<HR></BLOCKQUOTE>
Also, the process, the mechanism, that I'm asking about is what happens inside the metal, at the microstructural or grainboundary level, that causes the stresses to be relieved by cryo temperatures. I haven't seen anything, yet, that explains how very low temperatures can relieve stresses in metals. Anecdotal testimony is not an explanation.
The link that you provided has so many misconceptions in it that it's pitiful. Cryo treatment might very well produce more martensite and reduce the austenite, which would make the steel harder, but I'm convinced that the reduction in residual stresses actually occurs AFTER the cryo treatment when the temperature is cycled from room temperature to +300ºF and back to room temperature three times. The cryo hype even says that without the final heating to +300ºF and back to room temperature, then there is little or no benefit.
Other cryo-treatment hype also claims (not in your link) that music CDs, audio cables, and recording cartridges sound better after being cryo treated. Yeh, right. I waiting for some of the proponents to claim that it cures cancer, too.