Cryogenic Stress Relief

[Paradox]

There is no doubt that stress relieved automotive parts benefit (blocks, crankshafts, connecting rods, brake rotors, etc...). However, I have heard mixed reviews about using the cryogenic treatment process.

JP supports Cryo-treatment for his barrels, but has anyone done tests to support the claims? I know there is more to the treatment than a simple freeze to sub-zero temperatures. From what I have read, the process is similar to annealing, but you don't get some of the bad side effects such as removing scale/oxidation.

I have been looking into using a different type of stress relief for machined or welded parts... But waiting on procurement of the equipment to do so. The benefit is that a small shop could preform the operation faster and at much lower cost.

Long story short - do the cryogenic treated barrels work as advertised, and if so -are they worth the effort? If the same effects could be duplicated and at a much lower cost, would individual gunshops be interested? (This would apply to any machined or welded part - frames, slides, barrels, you name it.)

Personally, I think that frames and slides would benefit more from stress relief....

[Merlin Orr]

Jim Anglin does a lot of cryo stuff to his guns. He is a believer. And he sends his stuff out so there is at least Some market..

[EricW]

To my knowledge, no one has EVER done a double-blind experiment on a statistically significant batch of barrels - like say 10 of each. There's a bunch of anecdotal crapola out there that says "I cryo'd this barrel and boy does it shoot nice."

Well, a hell of a lot of untreated barrels have shot nice in the past. The question is "on average, does cryo treating produce a statistically detectible improvement in barrel performance?"

I've never seen it done. I never expect to. And I'm very confident I know the reason why.

I would also like to add that cryo-treated screwdriver bits are worthless garbage.

[/Cynical Skeptic Mode]

[PhilTerry]

The NRA reported a statistical double blind experiment in "The Rifleman" two or three years ago and concluded that there was no benefit when the shooter didn't know that that barrel had been treated. However, when the shooter was aware and knew which barrels had been treated and which had not, there was a statistically significant improvement in accuracy!

[Heath]

Dan Lilja has some opinions on the cryogenic stress relief of barrels here:

http://www.riflebarrels.com/faq_lilja_rifl...m#deepcryogenic

The short version is that it can't hurt, but that there aren't significant noticeable benefits to accuracy.

[BrianH]

What are you making , Paradox? And out of what?

Most barrels are made out of 416 which wouldn't really benefit from cryo treating.

[Paradox]

The Dan Lilja article pretty much mirrors what I initially thought about the process. My 'Cynical Skeptic Mode' was/has been on too, but I wanted to get opinions before introducing my bias

The process I was referring to is called "sub-harmonic vibrational stress relief".

VSR has been in use for several industrial applications, and I have heard positive results for those that tried it. However, I haven't seen use in the commercial firearms industry. If a rifle barrel did in fact benefit from stress relief, I would think VSR could be far more cost effective.

One of my good friends is a professional race engine builder, and some of his customers are requesting 'stress relieved' components. The parts are nodular cast iron, 4130 steel, A-356 Aluminum... and some others that escape me for the moment.

My father is an engineer in the metals industry, but they anneal their products. I spoke with him about VSR in a brief phone conversation... He thought the idea was "interesting" but he would need to see more information about it. If it looks promising, I might have a small VSR setup to play with...

[George]

The benefit that I understand Cryo treating barrels brings to the table is a lack of POI shift as they heat up rather than an increase in accuracy. IIRC, John at JP rifles told me that it won't make my AR more accurate, but that it will allow it to shoot to same POI from a hot barrel as it will from a cold barrel. I take that as a much better thing than a tiny (and possibly immeasurable) amount of accuracy increase. I also tend to think Cryo stress relief "will" actually have a measureable effect in this arena in comparison to the purported effect of increasing the ability of a barrel to hold a group "after" it is up to temp.

--

Regards,

[EricW]

I'm not from Missouri, but show me anyway.

[George]

It's not empirical, or statistically sound, but I sent a Remington bolter to JP for a brake and a cryo treatment. It used to put the first couple rounds in one group and the rest once it was hot into another. It shot MOA, it just shot 2 different MOA's. It now prints one group, cold to hot. It's still just an MOA bbl, it just only has one POI now. But and a very big but, it got re-crowned at JP to add the brake, so it's not the same barrel for several reasons now and the evidence is tainted to say the least.

--

Regards,

[Heath]

Any shift in POI from POA is a reduction of accuracy. Based on Lilja's article and as I understand it, barrels with residual stresses as a result of being button-rifled can be more prone to POI shifting due to heat. This is why Lilja and others using button rifling heat treat and stress-relieve barrels after rifling. Production barrels are cold-forged and have broach-cut rifling. These processes apparently do not build up significant residual stress and can be heat-treated anywhere along the process.

Further, Lilja writes, "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." If this is the case and the rifle does suffer from POI-shift do to residual stresses, then cryo-treating isn't going to completely solve the problem.

I am disinclined to believe that any kind of wonder process is going to improve accuracy without having seen significant research on the subject. The firearms industry is full of snake oil salesmen.

[GuildSF4]

The studies I have seen show longer wear time on cryogenic stress relieved tools. (It does depend on which process is used as to % extended life) deep treatment or shallow.

It also depends on the type of steel, S-7 deep treatment displayed average 500% life increase Vs non treated, T-2 showed 92% improvement for deep treatment Vs no treated. (Louisiana Tech University study)

I am not sure this would help on accuracy though.

[George]

Well, if heat treating removes "most" (*) of the stress related POI shifts and there is a further 6% decrease in that shift that is known to be removed from cold treating after heat treating, then it still sounds like a move in the right direction to do heat treating first and follow with cryo for the finishing touch. IMO, 6% is a "tad" more than an "insignificant" gain to me.

*I would like to see Leija's statement of "properly stress relieved with heat" defined as a percentage of total stress value removed for actual comparison purposes.

I am not saying I believe in a faith based manner that cryo improves accuracy. I am saying that there is a certainty that the effect cryo treating has on actual heat based POI shift in custom stainless barrels can be measured. In fact it seems to have been measured, at 6% ;-)

--

Regards,

[tightloop]

Dan Lilja says it is a toss up, if you like it, go for it..

[EricW]

I'll believe it, right after someone does a double blind test using at least 10 barrels in each configuration. I've heard and read this...well...I won't use the word I want...for years and years and it's always the same deal: a single data point with a user committed to demonstrating a predetermined result.

It's a great way to do science if you want to go far in the Sierra Club, but it's considered junk science everywhere else.

Do good science first ........ then promote the product. That's not too much to ask.

[Heath]

I'm not making the contention that cryo-treating has no discernable effect, just that it isn't particularly beneficial to accuracy in rifle barrels. Certainly, further stresses are relieved and it is more beneficial in other applications as GuildSF4 describes. Lilja mentions that it increases the useful life of the barrel somewhat, which could be beneficial, depending on the cost of the treatment. He also mentions that it improves machinability for some reason that isn't well understood. This point bothers me as it seems like it would be a simple matter to examine the crystalline structure of the metal pre and post cryo treatment and draw some conclusion about the differences. As Eric stated, though. It wouldn't be difficult to qualify the benefits using scientific methods. I don't believe that anyone has done this to date.

[Paradox]

I'll believe it, right after someone does a double blind test using at least 10 barrels in each configuration.  I've heard and read this...well...I won't use the word I want...for years and years and it's always the same deal:  a single data point with a user committed to demonstrating a predetermined result. 

It's a great way to do science if you want to go far in the Sierra Club, but it's considered junk science everywhere else. 

Do good science first ........ then promote the product.  That's not too much to ask.

<{POST_SNAPBACK}>

Amen.

[Heath]

I found an article on Brownell's site that refers to the benefits of cryogenic stress relief in tooling:

http://www.brownells.com/aspx/NS/GunTech/N...x?p=0&t=1&i=478

It's an interesting read. Apparently, cryo-treatment can produce some amazing results on the wear resistance of tool steels.

[Carlos]

Key word: tool steels: GuildsF4 wrote: "S-7 deep treatment displayed average 500% life increase Vs non treated,"

Difficulty is that: barrels are, in general, either 416 stainless or chrome-moly.

What USPSA parts are made of S-7 tool steel? SV hammers & sears. My SV hammer has cracked & been welded twice. Hooks are still in good shape though. It was formed useing a NO stress machining process (EDM).

IF there is a benefit to cryo, then it would appear to most benefit:

-non stainless steels

-steels that may retain the most residual stress such as hammer forged or button rifled barrels.

D.C. Johnson

[Carmoney]

Is a person who performs this sort of treatment called a "cryopractor"?

Mike

[spd522]

I had a Ruger M77 in 7mm mag. It never shot to my satisfaction so I floated the barrel( improved some) and added a timney trigger (better still) but it was still a 2.5" @100 gun at best with premium ammo. I tried several brands and bullet weights to try to find what it liked.

Finally I sent the barrel for the cryo treatment. Once back, I was able to get sub 2" groups and occasional 1.5" groups with the same ammo I tried before.

So although I believe the cryo treatment did improve the accuracy, it wasn't to the level of accuracy I expect from my hunting rifles so I sold it.

[Flexmoney]

I've had my head in the freezer all day...I haven't experienced any stress relief yet. I think I'll go try the oven for a while.

[Carlos]

Flex- we all know that shooting a USPSA match relieves stress. But if you shoot a match in sub-zero teperatures, will you realize greater stress reduction?