[rothamber]

I've been reading with interest the Superior Barrels info over on ARF.com. The Hard Blue process seems very interesting but after speaking with those guys on the phone, they are interested in applying the process to anyone elses barrels. Since then I've been trying to learn more about other bore treatment options. I spoke with Ryan with Ionbond's customs shop in NC, and he said their DCL coating is line-of-sight only and thus can't be used on the bore.

I know some manufacturers use the QPQ nitriding type finishes (Melonite, Tenifer, etc) such as Glock, and I am aware that POF and LWRC are using nitrided barrels in their uppers, but I don't know of anywhere I could send some of my barrels for treatment.

The basic idea here is to have barrels made to the appropriate specs, break them in for optimum acccuracy and then have them treated to preserve them as long as possible. With the current political environment, I frankly don't know about the availability of anything "AR" in the next few years. Of course if the treatments were to decrease accuracy by disrupting the bore in any way, that would be counterproductive.

Does anyone have any experience with any of these or other treatments positive or negative, or know where I could have some barrels treated?

Thanks in advance!

 

[constructor]

I've been reading with interest the Superior Barrels info over on ARF.com. The Hard Blue process seems very interesting but after speaking with those guys on the phone, they are interested in applying the process to anyone elses barrels. Since then I've been trying to learn more about other bore treatment options. I spoke with Ryan with Ionbond's customs shop in NC, and he said their DCL coating is line-of-sight only and thus can't be used on the bore.

I know some manufacturers use the QPQ nitriding type finishes (Melonite, Tenifer, etc) such as Glock, and I am aware that POF and LWRC are using nitrided barrels in their uppers, but I don't know of anywhere I could send some of my barrels for treatment.

The basic idea here is to have barrels made to the appropriate specs, break them in for optimum acccuracy and then have them treated to preserve them as long as possible. With the current political environment, I frankly don't know about the availability of anything "AR" in the next few years. Of course if the treatments were to decrease accuracy by disrupting the bore in any way, that would be counterproductive.

Does anyone have any experience with any of these or other treatments positive or negative, or know where I could have some barrels treated?

Thanks in advance!

I have talked to nearly every barrel manufacturer(not assembly companies but real manufactures) in the country in the last 4 months about this. They all told me any type of heat treatment will change the specs of the barrel and possibly induce stress and change the straightness of the barrel. When barrels leave the manufacturer they have been QCd for tolerance and straightness, if the QC department is doing their job the barrel should be correct and should not be contoured or changed in any way. Lothar has done extensive testing with Cryo treating to remove stress also, they tell me it removes only 7% of the stress in a barrel. So IMO all those people paying for Cryo are wasting their money at least when rifle barrels are concerned.
I have 10 chromoly barrels coming that I will send 2 for each different process including chrome lined, I will test them myself for accuracy, hardness and long term wear. If Art and actually get together we want to submit the best barrel available.

 

[marinesg1012]

I have a barrel I twice dunked in the cryo and it doesnt change POA and POI.... it is a 556 barrel that has a 4.5 inch group at 600 meters......

 

[T.Rexford]

I've spoken with a fair amount of people on Cryo. All my CPM154 blades get cryoe'd because if you've got the setup what the hell else are you going to do with it? What I know from it, as far as barrels, high performance engine parts, and knives are concerned is that the jury is still out on its effectiveness but no matter what the steel does undergo a change. The idea is to change the little austenite that is left over to martensite.

Does it really make a difference? Well it may, but you may never notice it. Its also possible that the difference it makes is that a part that would have broken does not. This latter statement from my limited knowledge is what I believe to be true.

Now the bottom line though is that it does not take that much to do the cryo soak and like I said before if your set up to do it then do it. There's hardly any labor involved.

 

[constructor]

So if you buy a barrel for $179 that has rumble strips in the bore then spend $50 to cryo it will it shoot better than a $230 barrel of better quality?

 

[T.Rexford]

Well barrels are a bit out of my league but here goes...

The trick to Cryo is you want it to be done at a certain time. Basically for me it goes like this. Heat treat and soak at temp per alloy. Quench in either oil or air quench in aluminum depending on alloy. Cryo quench. Then temper.

The reason for this is because the cryo quench will turn some of the leftover austenite to martensite and you want all of it tempered. If you cryo after temper then you have just reintroduced a possible stressor into the steel again. The idea is to have all of the martensite at the same hardness.

Also the colder the cryo the better. So Liquid Nitrogen is better than dry ice.

Now harder steel = higher wear resistance to a certain extent. For a knifemaker any percentage change is worth it. For a gun barrel I could see the barrel lasting longer before it was shot out. I don't see any reason why it would improve accuracy except for these two possiblities: As the bullet is traveling down the barrel the coefficient of friction between the hardened steel and the softer areas could create an uneven drag but this is kind of ridiculous. We're talking minuscule areas of change here. The other idea is more realistic IMO. The harmonics generated by a barrel that has been cryo could be more even. Hopefully a metalurgist could chime in on this.


Constructor: I didn't really understand "rumble strips"

 

[T.Rexford]

Just found this article as I wanted to research it more:

Good read discussing barrels directly and it seems it was pretty much common sense as to what Lilja believes is the case.

http://www.geocities.com/felixthefish.g ... tment.html

 

[constructor]

So here is another barrel maker saying the claims made by some are unfounded-
Quote Dan Lilja-"The cryogenic treating of barrels at a temperature of -300 degrees below zero [77K] 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."

That is another opinion that if you cryo a barrel after the manufacturing process you are wasting your money, spend the $50 on something that actually does something, half of a trigger cost or a better barrel to start with.

 

[T.Rexford]

Now I think we can agree cryo is not going to increase accuracy. Anybody with a barrel thinking of having cryo done IMO is 1) doing it at the wrong step of the process, and 2) wasting money.

BUT on that note I'm not willing to throw cyo under the bus as far as barrels go. If you've got the setup as a manufacturer just do it. Its easy. And two if it increases barrel life which my gut feeling is it will (I have no idea what kind of round count though) then that is a benefit. For the cheap cost and the ability to do no harm whatsoever during the process then what the hell.

 

[Test_User]

Oh come on even if I let you drive the bus? :mrgreen: You can even drive it really fast and we can pout mad max type wheel hubs and everything on it. :lol: :lol:

 

[rothamber]

Thanks for the replies, guys. I'll be eager to see how Constructor's research goes on the different barrel treatments. I certainly wouldn't want to warp a high dollar barrel with one of these high temperature treatments. Again anything detrimental to accuracy would defeat the purpose. If I were going to sacrifice accuracy it would probably be easier and less expensive just to get a chrome lined barrel.

 

[rothamber]

I just got off the phone with Andy Russel of Metcor regarding their Melonite QPQ process and he felt that, although it would decrease the coefficient of friction, the high temperature of the Melonite nitriding process would likely significantly decrease the hardness of the steel and wouldn't be worth the risk of ruining the barrel. Note that he said that they had not actually tried the process on a rifle barrel, but he didn't seem too enthusiastic. I think I'll just wait and see what Constructor comes up with.

 

[Test_User]

I found this very interesting tid-bit on Nitro-Carbonizing which might very well explain one of the issues with barrels using this treatment in their bores.: This is off one of the leading Nitro manfuc sites: It states that for surfaces that are expected to need low friction such as load bearing surfaces (like a barrels bore)the surface needs to be polished/burnished after treatment as the process causes the surface to be roughened up. So I would strongly suggest a thorough break in process for any barrels using this. The kind of shoot 1 and clean until you don't get fouling then 2 and clean and so on up to 10. It also says that the parts should be throughly stress relieved before the process to prevent any changes. The thickness of the process is linked to length of time of the process and the carbon content. But .0003 minimum to .001 max growth of dimensions. The rest of the characteristics are very favorable!! IMHO messing with the bore of a finished barrel with a process that requires higher or longer duration heat then that of typical shooing is going to have its trade offs. They may very well be worth it depending on the main goal.

 

[rcrandall]

I thought I would bring thread back because I'm thinking of sending a barrel to Coal Creek Armory for the Melonite process. Any word on barrel testing with this process?

 

[marinesg1012]

what barrel are you going to send?

Let us know how it works out if you do it.

 

[marinesg1012]

I have 10 chromoly barrels coming that I will send 2 for each different process including chrome lined, I will test them myself for accuracy, hardness and long term wear. If Art and actually get together we want to submit the best barrel available.

H-

Did you do this and if so how did it work out?

 

[rcrandall]

I was going to send my stainless AR15 Performance 12 twist 3 groove barrel but I'm wondering if I want to risk such a beautiful barrel. The cost was about $75.00. They also do this process on parts.

 

[Test_User]

Are you speaking of doing the outside or inside of the bore. If inside I would strongly recommend against it. That is a match barrel not a combat grade barrel. If its for the outside why not go with Cerro Kote as it not like barresl get huge amounts of abuse. 3/4 is covered wit th HG. I do not like the idea of heating up a finshed match barrel to higher temps then it gets from regular shooting.

 

[rcrandall]

Yeah, I think I'll just decide on a finish for the outside of the barrel and not worry about it.