Turning Material Off of a Heavy Barrel

[I Dont Care About You]

what indemnification does the gunsmith activity provide you with?

Indemnification? None, except maybe to protect you from your government.

Cryogenic treatment does little is anything to relieve stress within the steel, though it may aid in machinability. Stress relief, or normalizing is done with heat.

Thats not true. Years ago I did a pseudo scientific study of cryogenic treatment of rifle barrels. We tested a half dozen different rifles of different quality and caliber. The basic result was that cryogenic treatment didn't greatly improve really good barrels, likely because they had less internal stresses. The cryo treatment did significantly improve lower quality barrels, likely because they have a lot more internal stresses.

It is against the law to work on a firearm and charge for that work if you don't have the federal license allowing you to do so.

Not doubting you, but where does it say this in the law?

 

[guntech]

I agree with Mr. Leeper. With the majority of barrel makers stress relief is done with heat treatment not Cryogenics. If a barrel is not stress relieved that will show up when the barrel is turned down in a lathe. Cryogenic treatment is a relatively new process used on barrels to supposedly improve accuracy.

As far as a federal license for gunsmithing goes, call your Provincial Firearms Officer and ask them. https://rcmp.ca/en/firearms/contact-chief-firearms-officer

 

[apexanimal]

I have used an XCR in the past with a heavy barrel that a gunsmith turned the end down quite a bit, made the rifle much more manageable and comfortable to use standing and kneeling and getting up from prone faster. My main use was shooting steel silhouette gongs up to 350m. I didnt notice any reduced practical accuracy from before to after. If your use case is something similar to mine, you will notice no downsides to reducing the barrel weight. If your goals are more ambitious than mine, i cannot speak to whether the pros and cons will work out for you. Another option i didnt have due to the proprietary nature of the xcr barrel at the time, is just selling your heavy bbl and buying a lighter one more to your liking. Thought id add some first hand anecdotal experience in case you got tired of hearing about stress relief and "harmonics", which are interesting topics but for the majority of AR shooting, pretty irrelevant. This has just been my experience.

 

[mmattockx]

Another option i didnt have due to the proprietary nature of the xcr barrel at the time, is just selling your heavy bbl and buying a lighter one more to your liking.

I have considered that, but the barrel shoots decently for me and new barrel prices have gone up a lot in the last few years. It's somewhat a bird in the hand situation. I have a friend who can do the turning for me, so cost is minimal and I wanted to know if there was any longstanding experience that says turning the barrel has a high chance of hurting the accuracy. Sounds like that is not much of a concern, though, so I will probably go ahead and give it a shot.

Thought id add some first hand anecdotal experience in case you got tired of hearing about stress relief and "harmonics", which are interesting topics but for the majority of AR shooting, pretty irrelevant.

I'm an engineer, so I don't mind the geekery at all, but practical experience is also very welcome.


Mark

 

[wrangler4867]

Yeah, that's fantastic, if you happen to have a $50,000 CNC milling machine with a live 4th axis. Weirdly most people don't.

I do, but all the plugs in my house are 2 prong, and I don't want to snip the ground pin off the cnc plug.

 

[Silverado]

 

[I Dont Care About You]

I do, but all the plugs in my house are 2 prong, and I don't want to snip the ground pin off the cnc plug.

A decent CNC machine will require 2-phase 220v at least. Kinda different plug than household 3-prong.

 

[Lakkenbak]

I agree with Mr. Leeper. With the majority of barrel makers stress relief is done with heat treatment not Cryogenics. If a barrel is not stress relieved that will show up when the barrel is turned down in a lathe. Cryogenic treatment is a relatively new process used on barrels to supposedly improve accuracy.

As far as a federal license for gunsmithing goes, call your Provincial Firearms Officer and ask them. https://rcmp.ca/en/firearms/contact-chief-firearms-officer

Cryogenic treatment is used to reduce retained austenite which makes a more stable microstructure, resulting in less stress, and harder steel.


https://knifesteelnerds.com/2018/12/03/cryogenic-part1/

 

[wrangler4867]

A decent CNC machine will require 2-phase 220v at least. Kinda different plug than household 3-prong.

Did we not notice the laughing emoji?
If you want to get technical. There is no 2 phase. There is single phase or 3 phase.
You need 3 phase to achieve 120/208, or 347/600v, single phase gets you 120/ 240 found in residential.
I made the joke because I used to be an industrial electrician in a past life.

 

[guntech]

In rifle barrel manufacturing, "stress relieving" refers to a heat treatment process where a barrel blank is heated to a controlled temperature after rifling to remove internal stresses created during machining, particularly from cold forming methods like button rifling, ensuring the barrel maintains its shape and accuracy when further worked on and used in a firearm; this is usually done in a vacuum furnace to prevent decarburization of the steel.

Cryogenic treatment of rifle barrels is not used in the manufacturing process. It is a "after" process that may increase accuracy and decreases shot dispersion. It is used for stress relief and to improve the microstructure of the barrel. While some companies have embraced this technology, it is not widely used.

 

[Jonnyofalltrades]

While some companies have embraced this technology, it is not widely used.

Not to mention outrageously expensive if doing a single barrel.

 

[blargon]

I had Bill Leeper turn a #7 shilen barrel to a #1 and its a tack driver on a 5.75lb rifle.

 

[tiriaq]

Years ago, in Precision Shooting magazine, there was a surge of interest in cryo-processing precision barrels.
Apparently cryo-processing was being used extensively in the manufacture of industrial cutting tools. Just the other day I saw that it is used in the manufacture of razor blades.
No idea if this is relevant to the OP's Shilen barrel, whether the barrel was cryo-processed.
One topic that hasn't surfaced is what difference it would make if the barrel were nitrided. OP didn't mention this, I don't know if this is something Shilen did. I've never tried to machine a nitrided barrel.

 

[mmattockx]

No idea if this is relevant to the OP's Shilen barrel, whether the barrel was cryo-processed.

Not that I know of.

One topic that hasn't surfaced is what difference it would make if the barrel were nitrided. OP didn't mention this, I don't know if this is something Shilen did. I've never tried to machine a nitrided barrel.

Barrel is stainless and is not nitrided that I am aware. It looks to be bead blasted raw stainless from its appearance.


Mark

 

[tiriaq]

As I've posted previously, turning this barrel down to reduce its weight should be a straightforward operation. Smooth the turned surface, into the blast cabinet, and it is finished.

 

[I Dont Care About You]

I've never tried to machine a nitrided barrel.

I have worked on nitrided barrels. Nitriding is very thin so it is just the outer surface you need to get through. It is tough on HSS tooling but carbide tooling cuts through it fairly easily.

 

[Jonnyofalltrades]

I have machined thousands of nitrided shafts. No nitrided barrels, just shafts.
It cuts easily with carbide tooling. About like breaking through chrome plating.