Superalloy barrels

[lysander]

As I posted in the quoted link, the benefit of nitriding a barrel is removed if the nitrided layer of the bore must be removed to allow chrome plating (not uncluding the benefit of the outside of the barrel being nitrided).

My curiosity comes from whether the nitrided layer within the bore must be removed to allow chrome plating to begin with, or if something can be changed in either procedure to allow the to barrel finishes to be applied and have thier effects remain inact to additively applied.

You say that a barrel can be nitrided and then chrome plated, assuming the nitrided layer within the bore remains intact and the chrome plating applied over it, why, exactly, are the effects not cumulative or additive?

Your second pargraph in the post I quoted does not help me understand. I am not trying to be obtuse, but I do admit to having not read up on the subject in some time and being not as interested in the topic as I once was.


And no, I do not subscribe to the line of thinking that just because it's not being done that way that it means that it's already been tried, tested and found wanting. I need a bit more than that.

Well, the M256 is a smooth bore tube, so it is of no particular problem to machine them oversized to accommodate the additional thickness of chromium. Since nitriding adds no additional thickness, there is no reason to remove the nitrided surface in order to plate it.

As to why they don't use it I cannot give an answer, other than to offer these two choices, 1) all the major caliber gun manufacturers, BAe North America (formerly United Defense), General Dynamics (Saco), Alliant, Mesa and Watervliet Arsenal as well as all the small caliber barrel manufactures like Colt and FN are complete idiots; all willing to spend millions of dollars since the late 1970 on things like explosive tantalum cladding or plasma spray as alternatives instead of a relatively inexpensive and simple plating over nitride, or 2) there is some technical reason why it is not worth the effort. You can pick your favorite.

There are many reports on how to increase barrel life published by the USG out there free for the reading, there are also as many more that are not released to the public.

[BufordTJustice]

Obviously, a stellite liner for the chamber, throat, and first few inches of barrel would allow for higher rates of fire (and, ostensibly, longer life), but the liner would be virtually impossible to machine on any kind of production scale/pricing structure.

Does anybody know what alloy Hodge Defense is using?

[Biggy]

Obviously, a stellite liner for the chamber, throat, and first few inches of barrel would allow for higher rates of fire (and, ostensibly, longer life), but the liner would be virtually impossible to machine on any kind of production scale/pricing structure.

Does anybody know what alloy Hodge Defense is using?

I believe the steel alloy Hodge Defense is using for their CHF barrels is 9310H .

[lysander]

Stellite liners bring a few problems of their own, such as lining up the rifling between the liner and the rest of the barrel.

However, stellite lined machine gun barrels have been used for years.

[nova3930]

Well, the M256 is a smooth bore tube, so it is of no particular problem to machine them oversized to accommodate the additional thickness of chromium. Since nitriding adds no additional thickness, there is no reason to remove the nitrided surface in order to plate it.

As to why they don't use it I cannot give an answer, other than to offer these two choices, 1) all the major caliber gun manufacturers, BAe North America (formerly United Defense), General Dynamics (Saco), Alliant, Mesa and Watervliet Arsenal as well as all the small caliber barrel manufactures like Colt and FN are complete idiots; all willing to spend millions of dollars since the late 1970 on things like explosive tantalum cladding or plasma spray as alternatives instead of a relatively inexpensive and simple plating over nitride, or 2) there is some technical reason why it is not worth the effort. You can pick your favorite.

There are many reports on how to increase barrel life published by the USG out there free for the reading, there are also as many more that are not released to the public.

to know exactly why it's not done you'd have to know the exact requirements spec for the item in question. could be different in each one. I wouldn't even swag at an answer though

Sent from my SAMSUNG-SM-G930A using Tapatalk

[lysander]

to know exactly why it's not done you'd have to know the exact requirements spec for the item in question. could be different in each one. I wouldn't even swag at an answer though

Sent from my SAMSUNG-SM-G930A using Tapatalk

Note that it is not done for small arms barrels either. They still use just chrome plating, M4s, M16s, M249, M110, etc. Yet, this application is also subject to millions in research for ways to improve barrel life....

[nova3930]

Note that it is not done for small arms barrels either. They still use just chrome plating, M4s, M16s, M249, M110, etc. Yet, this application is also subject to millions in research for ways to improve barrel life....

oh yeah I know. was just adding some to your point. There's some reason it isn't done but real hard to know what that reason is

Sent from my SAMSUNG-SM-G930A using Tapatalk

[vicious_cb]

Stellite liners bring a few problems of their own, such as lining up the rifling between the liner and the rest of the barrel.

However, stellite lined machine gun barrels have been used for years.

Fine for a MG barrel but the decrease in accuracy wouldn't be worth it in a rifle or carbine nor the decrease in corrosion resistance.

In the history of the Ordnance Dept. the research personnel were always looking for ways to extend bore life and help stop corrosion. Plated and lined bores were the answer. A plated bore is one which is chrome plated, usually from the beginning of the chamber to the muzzle. This helps fight the battle against rust and gives the bore a considerably longer life. A lined bore is one which has a 9 inch stellite liner, which starts at the end of the chamber. Stellite is an incredibly hard material and was used only in machine gun barrels. Aircraft machine gun barrels with stellite were rated at 6-7000 rounds of life, versus 1500 for unlined barrels of the same type. Stellite, although it does not have the same resistance to rust as chrome, will extend barrel life far beyond that of chrome.

[vicious_cb]

Here is some light reading on the subject of the .mil testing various barrel linings/platings for 5.56 SAW barrels.

http://www.dtic.mil/dtic/tr/fulltext/u2/822736.pdf

[lysander]

Here is some light reading on the subject of the .mil testing various barrel linings/platings for 5.56 SAW barrels.

http://www.dtic.mil/dtic/tr/fulltext/u2/822736.pdf

Actually, the testing in that report was done with the Stoner 63 belt fed machine gun, XM207