I see Benelli lists this for their R1 rifle barrels.

It is supposed to stabilize the crytalline structure of the steel thereby reducing or relieving stress. Lots of debate on whether it works or not. Krieger (and some others) offer this on their barrels. It also supposedly makes the steel more durable.

among the most precision pieces of steel in the world are industrial gauge blocks.....many of these sets are made to tolerances of +/- .000002 or 2 millionths of an inch.

Cryogenic treating was used to help stabilize the metal in the making of these precision blocks used for gauging and tracability to the National Bureau of Standards. It's well documented that this "heat treating" process has benefits.

It's never been proven to do a thing for rifle barrels however.

That said many folks claim it makes it easier to clean their barrels.

Takes time, costs money and adds no value. Kinda like a democrat!-Rob

quote:

Originally posted by Robgunbuilder:
Takes time, costs money and adds no value.

There is not scientific data that supports that it is beneficial. In my opinion it is a last stab in the dark to get a gun to shoot. Save your money what you spend will pay for 30% of the cost of a new barrel which is where you are headed anyway.

I know someone who sent several barrels to be cryo'd. Most didn't change, some got better and some got worse accuracy-wise.

One wag on another website posted that if you sent him your barrel and $50.00 dollars, he'd take it to a topless bar and pour every second beer thru your barrel. He said that he figured that ought to relieve some stress.

The photographs of cryo'd and uncryo'd barrels on the Benelli website are nonsense ,Certainly no metallurgist made those statements [ this is annoying since they make great guns !] The NRA tests and tests by others find no difference . I'm amused that the companies that do it refer to a technical paper which has to do with a complex tool steel which has nothing to do with a rifle barrel. Save your money.

Several years ago I was at Hart Rifle Barrels and talking to Mr B Sutton on the subject. As he put it, it reduces up to 7% of the residual stress after stress relieving... about no change. Not worth it according to that source.

It's commonly used on high quality knives - less commonly used on brake disks as well.

It's a 'toughness' thing for the knives. I don't understand the metalurgy behind it completely, but it's something to do with the crystaline structure of the steel. It does make a difference in both knives and brakes - so I suspect it'd do something for a barrel.

Bob, not a good conclusion since high quality knives [complex steels], brake discs and barrel steels are very different materials and will react to things like cryo very differently !

Hello,
Several years ago, freezing the barrel was popular by match shooters and the cost then was some 50.00 or so to have it done and the wait time was about one week, so lot of people did it, including myself. As mentioned, supposedly aids in ridding stress or "relief" if you will, and it may well do that, but first barrel I had it applied was a factory varmint style 700 in 308. Upon return and test firing, first few shots were spaced out as they say and worrysome. Called the shop and they mentioned that the original grouping would be "different" and to keep shooting and if after a few more rounds it did not return to good groups, etc. let them know. Well, took about 45-50 rounds and sure enough the rifle began producing excellent groups. For my long range rifles, will normally use the Krieger barrels due to outstanding performance and long life and the ones I had/have were double frozen, prior to drilling, and after drilling and rifling. Does it work?? I don't think it hurts for the Kriegers are about as good as they get these days. Kind of like you "pays your money and takes your chances..."

Cryogenic thermal treating was primarily born in the cutting tool industry to stabilize tools dimensionally and to increase the wear. In this case depending on the amount, morphology, and location of retained (non-transformed)austenite, which can transform during heating/pressure, can induce non-tempered martenite during machining. In higher carbon steel alloys, this results in a 2.4 % volume expansion during the A to M transformation in addition to the residual stresses from the untempered martenite. The contact and thermal stresses at the active cutting tip are tremendous, thus resulting in this behavior.

Now, this documented behavior was applied to all sorts of materials, steel and Al alloys, some with success, sometimes not. Due to the complexity of each individual alloy system, thermal and quench treatments, fixturing during heat treatment, tempering temps, times, sequence, etc, etc, etc,, the beneficial results were varied.

From my days as a research metallurgist and later an engr metallurgist in the aerospace and tool business, I have seen companies and marketing specialists promote the effect of cryogenic treatment as some sort of black magic. Usually, a purchasing dept will be interested in this magic fix.

Now to rifle barrels: Most barrels are probably Rc 40-45, probably from 4135-4140 steel or a modified high Mn 1040 steel. If they are thermally stabilized during heat treatment, and if abusive machining techniques are not used, chances are little that cryogenic benefit will result. But if the barrels are quench and tempered and uneven quenching will produce non-symetrical distortion stresses, then a treatment may be helpful. I would quess some barrels are machined directly from hot or cold rolled stock--leading to big variances in any effects.

BUT, what accuracy advantage will a .000001 mm in distortion correction result in ???? Or does a properly broken-in barrel take care of any residual temsile/compressive stresses???

In the lab, we used liq N2 heat treatments as a normal procedure to assist in the transformation of highly alloyed austenites, particularly in highly alloyed structural and tool secondary hardening steels.

Well enough of this! But trying to give everyone a view of the role and complexity the alloy, manu processing, heat treating, and machining history can have on this issue.

So everyone, with all the anecdotal evidence, could be right or wrong in each case---all depending on your ability to measure differences and your belief in magic.

DAK, PhD

quote:

industrial gauge blocks

wow vap, you know what these are...i had to use these when i was working for my dad in his machine shop...brought back memories...

quote:

Originally posted by Robgunbuilder:
Takes time, costs money and adds no value. Kinda like a democrat!-Rob

my vote for funniest post of the week!

great posts everyone...

this gets my "Thread of the week" vote too!

the cryo thing is more mental and acts more of a dollar separating function and bragging rights thing.