Cryo Treating to Remove Stress?

[John11-87]

Hey guys im hoping some one can point me in the right direction here.

So im one of those guys who can leave well enough alone.... we will start with that. I have a old 6br barrel (Pac-Nor 8 twist, around 4000 rounds) that i took off my long range br rig and put on a remington action to use as a occasional varmint shooter. The thing shot really good anywhere from .2 to .5 moa shooting the 105 berger hunting VLD. Any way being the barrel is a heavy palma contour i decided it would be a good idea to flute the barrel to make it light enough for me to comfortable shoot free hand, and being a machinist i just went ahead and did it. The barrel turned out really good and looks awesome i put 5 .255 wide flutes in 18 inches long, .125 deep( with a full radius in the bottom). Finally shot it again the other night same load same stock same everything, and i get strange groups. First 3 shots with be in the 2s or 3s and the next one goes high and right every time (an inch or more) and the shot after that does the same! Seems to me my machining did induced some stress in the barrel, even though i took very light cuts and kept it cool, so now when it heats up it throws shots?

My question is would a cryogenic treatment cure this barrel of this, or does it have to be "heat treated" like in an oven to remove the stress? Maybe im SOL i dont really know, i probably should have left well enough alone when i had a good shooter, but you know how it is :. Anyway im hoping someone can shed some light on this for me.

Thanks for looking!
John

 

[stebbins243]

Im not sure about the cryo treatment, i think its more for fracture treatment of steel after its initial heat treatment. It may help, but one thing for sure is the barrel needs to get stress releived again. When you cut the flutes you increased surface tension by creating more surface volume on the barrel, in doing so you introduced new stress into it. Thats why when the barrel starts to warm up the shots move so much.

 

[tome]

I guess the real question is..how many $$$$ do you want to put into a barrel with 4000 down the tube..a new pac-nor barrel chambered and pre threaded for the Remington is around $440.00

 

[fredhorace77]

imo..with no offense meant...u screwed it up...

 

[John11-87]

Thanks for the replies guys I appreciate it.

Fred, I think you are right... I did screw it up, but it was worthless to me as I was looking for a carry rifle... And the barrel was nearly done anyways.

Tome I guess if I could get it chryogenically treated for around 50 to 60 I would be willing to try it... Maybe learn something if nothing else.

I have to try something otherwise I just have a tomatoe stake! Maybe after treating it will be a real expensive tomatoe stake! Im going to call 300below today and get a price.

John

 

[doc gordon]

maybe set the barrel back?probably should take 1/2" off muzzle also !

 

[fdshuster]

John11-87: To backup what stebbins243 said, checkout Hart Barrels website, in the FAQ thread. They do all their outside machining before the final lapping.

 

[butchlambert]

It is time to cut your loses and make a tomato stake out of it. You may want to throw a little money at it and find out it is toast.
Give up guy!!

 

[dan06]

I would agree that it was time to cut your losses but I have seen the cryro treatment work on a barrel that would walk shots. I had a friend with a 6.5-06 that would group the first 3 shots into about .5 inches then every shot after that wend some to the right and about 3/4 inch higher. He sent it in to get the cryro treatment and it came back a good honest half moa gun for five shot groups. If I remember right it cost a little over 100 bucks with shipping.

 

[John11-87]

Thanks for the replies guys!

 

[BoydAllen]

Two questions...When you fluted the barrel, did you take a series of very light cuts, rotating the barrel to a new index position after each one? What type of setup and cutter did you use?

 

[John11-87]

Boydallen,

I did the work in a Mazak 4 axis turning center. .250 carbide 4 flute ball end mill .025 per pass at .0007 inches per revolution and then a finish pass at the final depth to clean the last .002 of material off he bottom and sides. Flood coolant the who time to keep everything Cool.

John

 

[BoydAllen]

Did you finish one flute before moving on to the next, or keep going around the barrel, bringing them all to depth together?

 

[John11-87]

completely finished each flute then indexed to the next.

John

 

[butchlambert]

Boyd,
I knew where you were going with this.

 

[John11-87]

Did i miss somthing guys?

John

 

[therifler]

well i do them alittle different i index the barrel on ruffing cuts in a specific manner .i really don't know if it makes a difference with the stress but the guns seem to shoot well .your machining procedure sounds good, however cutting a barrel that has been used as hard as yours, i'm not sure you could beat the stress anyway .no lab tested theories here just time tested method.
hope this helps in someway . T.R.

 

[butchlambert]

I think what Mr Burns is saying is to take a roughing cut or two indexing to the opposite side after each roughing cut. Skip Otto used to flute an ungodly amount of barrels. Skip had a very large horizontal mill. He had a set up to do 4 barrels at a time. His tooling was set up to index them all at one time. He used flood cooling. After years of fluting he found you couldn't hog it off in one cut and you needed to go as close to the opposite side of the barrel each time.
I was in Phoenix several years ago when Skip shot the first "0" at 200yds in competition.

 

[BoydAllen]

I think that I would think about how you tighten down a cylinder head, or lug nuts. In the case of fluting, I would want to take it down in steps cutting a pattern that crossed center to near the opposite side, and rotated around the part, in several stages.

 

[therifler]

thanks mr.lambert and boyd exactly what i meant . T.R.