300 Below cryo process on my 338 lapua

[coyotezapper]

I have a Rem700 7mm STW that was a real fouler when I first got it. After 20 rounds accuracy went to hell. It would take upwards of ninety minutes to get the copper out. I then sent it off to 300 Below and had them cryo it. Cleaning / fouling is now minimal. Was this the result of the cryo treatment? Hard to say. It could be that the barrel was finally burnished properly. I have since lapped the bore with 3M polishing paper and fouling is similar to a custom tube. 1200 rounds now down the tube and accuracy is .5, .6 with two very different bullet types. I am curious to see how long the barrel will go. I expected it to be toast by now. I was told barrell life would be longer. Hmmm

 

[REDHEAD]

Thank You Kevin , it was Blackstar I sent my Weatherby to.lightbulb

 

[Nimrod]

I am a machinist by trade and have had to deal with stress related issues from time to time. From my observations stress is not actually caused by the machining processes but is induced in the manufacture of the material. The machining process simply brings it to the surface, for best results the material should be stress relieved before any machining process takes place. The stress relief process is usually done after the initial heat treating if there is any involved. It's hard to imagine just looking at a block of metal laying on a bench, how much stress can actually be involved but it can be significant. A particular instance I remember concerned a fair sized piece of titanium, I was doing prep work on it that consisted of facing both sides and putting bolt holes and counterbores down the sides. The material was about 7 or 8 feet long and around 24 inches wide by 2 1/2 inches thick. There was a thickness call out of 2.250 +/- .010 after machining, the material was as received from the vendor. The normal procedure was to face about .125 from the first side and and then flip the material over, face the second side to finish dimensions and drill/counterbore the holes. This particular piece of material was bowed in both directions, in the thickness plane it would have required nearly an inch of material removal to make it flat and in the long dimension the 3/4" bolt hole nearest one end would have been completely off the part. We sent it back to the mill to be stress relieved and it came back flat and straight to within a few thousandths of an inch. In this case I think the block was sawed from the end of a large plate and warped after sawing. Normally I see the most movement near the ends of a piece of material. The machining process will cause the stress to manifest itself, especially if material is not removed equally from all sides. In my opinion for cryo treatment to have any significant effect , it would need to be done prior to any metal removal. I used to work in a shop that bought a cryo tank to treat cutting tool inserts in an attempt to get more life out of them, it didn't work.

Sorry for the long post!

Hey Kevin, you guys don't need a machinist do you ?

Bob

 

[hoverp]

For the heat treating guys out there that relieve stress this way, what kind of temps are you talking about. If 300 below does -300 and +300 cycles would this not be considered heat traeting as well? or is +300 degrees way too cool to be considered heat treating?