Salt Bath Nitride Caution

[bozo699]

Awesome!!! I hope it continues to hold up for you.
Wayne.

 

[broncman]

For what it is worth, Once we chamber up a bbl that is going to be nitrided, it is not fired. We smooth up the throat area with lapping compound to remove the reamer/tool marks. Once they are smooth and mark free (borescope inspected), then they are sent off for nitriding. Haven't had one fail to be accurate and fouling free yet.

Bob

Bob, what do you use to work the lapping compound in the throat area? Heard thos before and was curious aa to what you use to apply and work the comound.
Kem

 

[bowfisher]

I had a nitrided barrel do the exact same thing. Couldn't figure out why it was a copper sponge. Upon inspection with the bore scope, it had pits and "gatoring". Barrel should have lasted forever...we sure scratched our heads over it.

Too bad it happened to you also, but I'm glad I finally got an answer,

 

[Bob3700]

Kem,

We take a worn bronze brush and wrap a patch around it. Imbed the lapping compound and go to work short stroking the lead area of the chamber.

You just have to work the are and then take a look with your borescope. You can see the reamer tooling marks running 90 degrees to the lands. As the lapping progresses, the tooling marks are polished away.

This technique has worked well for us as we have three bbls chambered this way and MMI coated. They all shoot very well.

Bob

 

[boltfluter]

Kem,

We take a worn bronze brush and wrap a patch around it. Imbed the lapping compound and go to work short stroking the lead area of the chamber.

You just have to work the are and then take a look with your borescope. You can see the reamer tooling marks running 90 degrees to the lands. As the lapping progresses, the tooling marks are polished away.

This technique has worked well for us as we have three bbls chambered this way and MMI coated. They all shoot very well.

Bob

Great info there. Thanks for sharing Bob. Will probably save a lot of people from heart break in the near future. Would you mind sharing the grit that you use for lapping? Thanks.

Regards, Paul

www.boltfluting.com

 

[Lazydays]

Had a brand new K barrel Nitrided after breaking in with 20rds cleaning between each shoot with SC and scrubbing with JB before treating, this thing was shiny clean. First 600 F match score was 568, my average is 590. The inspection with a borescope showed a solid copper streak on the top of one land from the muzzle to 4" in. After removing the copper I discovered a 1" line of pitting on the top of the land which was tearing the jackets. Sent the barrel back to K and this was there response today.
The pitting was caused by a reaction to the salt bath with copper left in the barrel before treating. But it was supper clean I said. Response was
It is theoretically impossible to remove all copper from a fired barrel due to the expansion and contraction from firing no matter how it is cleaned. Yours is not the only one we have seen with this.
$600 tomatoe stake. Just a heads up

I have no opinion on the subject matter, but thinking about it gives me a couple questions. A salt bath is exactly 1460 degrees (salt melts at 1460 degrees and is a known constant). A typical nitride process runs around 900 degrees (give or take a few degrees depending on the exact process). 1460 degrees is often used in a normalizing process and will actually soften some steels. Yet it's also used to harden some.

now a liquid salt bath looks to me like it would degrade the quality of the barrel. Am I right? There are various forms of nitriding. Some are plasma, some are gas injected and there is a third process which I can't remember exactly how it works. But that one uses amonia that is cracked. Am I wrong in my thinking here as well?
gary

 

[mstrophyhunter]

Bobr1 your new 260 is ready to ship will be on its way to you by Tuesday

 

[Bobr]

Thank you

 

[Bobr]

UPDATE:
Got around to playing with this barrel to see if there was any way to save it. Loaded up 50 rds of the Tubb 6.5 lapping bullet kit #1-5 and shoot them with cleaning between firings as in breakin. After the #3 grit was fired the amount of copper on the patch dropped off a bunch, which the bore scope showed.
The pit marks are 70% gone or smaller along with any color of black from the nitriding? It ain't pretty in there but better
Shoot a 5/8" 5 shot group with low vertical at 100 yards with a load picked on quick load from a wobbly bench, not the best but will report back after a load is worked up and a match is shoot.
If you have one don't plant the tomatoes yet
Bob

 

[rain164845]

I've watched BobR1 clean his guns many times and I will be surprised to find out he left any Kroil in his barrel as he always "flushes" with something similar to Gum Out to clean any residue of the Copper Cleaner or oil from the surface of the barrel before storing. I don't mean to speak for Bob just saying........

A according to Jim Borden, aerosol cleaners (brake cleaners?) Can hurt barrel steel.
http://www.google.com/url?sa=t&rct=j&q=borden%20rifles%20break%20in&source=web&cd=2&sqi=2&ved=0CCsQFjAB&url=http%3A%2F%2Fwww.bordenrifles.com%2Fclean.pdf&ei=pZ-_UdzIE5Lm8wT6lYDYDg&usg=AFQjCNEOo2UB2UpGFhCEYlQGZVCw49MbNA&sig2=B0Vqsp7d3RQVS0rZirsZ2g&bvm=bv.47883778,d.eWU

 

[butchlambert]

Had a brand new K barrel Nitrided after breaking in with 20rds cleaning between each shoot with SC and scrubbing with JB before treating, this thing was shiny clean. First 600 F match score was 568, my average is 590. The inspection with a borescope showed a solid copper streak on the top of one land from the muzzle to 4" in. After removing the copper I discovered a 1" line of pitting on the top of the land which was tearing the jackets. Sent the barrel back to K and this was there response today.
The pitting was caused by a reaction to the salt bath with copper left in the barrel before treating. But it was supper clean I said. Response was
It is theoretically impossible to remove all copper from a fired barrel due to the expansion and contraction from firing no matter how it is cleaned. Yours is not the only one we have seen with this.
$600 tomatoe stake. Just a heads up

I have no opinion on the subject matter, but thinking about it gives me a couple questions. A salt bath is exactly 1460 degrees (salt melts at 1460 degrees and is a known constant). A typical nitride process runs around 900 degrees (give or take a few degrees depending on the exact process). 1460 degrees is often used in a normalizing process and will actually soften some steels. Yet it's also used to harden some.

now a liquid salt bath looks to me like it would degrade the quality of the barrel. Am I right? There are various forms of nitriding. Some are plasma, some are gas injected and there is a third process which I can't remember exactly how it works. But that one uses amonia that is cracked. Am I wrong in my thinking here as well?
gary

You are wrong.

 

[CPorter]

Only gets to 1076 degrees according to this site:

http://www.northeastcoating.com/SaltBathNitriding_1.htm