AR15.Com Archives
 Stainless Steel Barrel
flyer8493  [Member]
7/21/2008 7:14:42 PM EST
I have an Olympic Arms M4 A3 TC (gay model name i know) that I recently realized was a SS barrel, before i just thought it was a chrome moly barrel. Anyways what are pros and cons for SS barrels. I did post this in the AR15 forum with 0 replies so now im posting here for exposure.
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Mall-Ninja  [Team Member]
7/21/2008 7:26:45 PM EST
SS barrels can be smoothed out more to give more consistent groups.
gdblair  [Member]
7/21/2008 7:29:22 PM EST
Tend to be more accurate than chrome lined.

flyer8493  [Member]
7/21/2008 7:30:39 PM EST
Thanks, are they more or less resistant to corrosion than chrome lined?
Jammer1  [Member]
7/21/2008 7:31:15 PM EST
Being harder than chrome-moly steel, it is more resistant to wear and generally resists throat erosion better. Then of course there is the obvious corrosion resistance improvement.
SkilletsUSMC  [Team Member]
7/21/2008 7:34:51 PM EST
Heres a post I made with the same question
gdblair  [Member]
7/21/2008 7:35:33 PM EST
I'm waiting for someone to come out with a stainless bbl with titanium nitride bore.It would be slicker, more accurate , and more resistant to corrosion than chrome.

Mall-Ninja  [Team Member]
7/21/2008 7:54:47 PM EST

Originally Posted By flyer8493:
Thanks, are they more or less resistant to corrosion than chrome lined?


Note that chrome-moly barrel does not equal chrome lined. They CAN be chrome lined, but not always.
Tolip  [Team Member]
7/21/2008 8:02:49 PM EST

Originally Posted By gdblair:
I'm waiting for someone to come out with a stainless bbl with titanium nitride bore.It would be slicker, more accurate , and more resistant to corrosion than chrome.



Why isn't titanium used more? Does it have unfavorable properties or is it just too expensive?
gdblair  [Member]
7/21/2008 8:11:35 PM EST

Originally Posted By Tolip:

Originally Posted By gdblair:
I'm waiting for someone to come out with a stainless bbl with titanium nitride bore.It would be slicker, more accurate , and more resistant to corrosion than chrome.



Why isn't titanium used more? Does it have unfavorable properties or is it just too expensive?

It's cheap enough for every kind of drill bit you can find .Superior to chrome in every way.

-It would be more expensive than chrome because you would have to start with the stainless steel to do the Tin process.
Tolip  [Team Member]
7/21/2008 8:15:56 PM EST

Originally Posted By gdblair:

Originally Posted By Tolip:

Originally Posted By gdblair:
I'm waiting for someone to come out with a stainless bbl with titanium nitride bore.It would be slicker, more accurate , and more resistant to corrosion than chrome.



Why isn't titanium used more? Does it have unfavorable properties or is it just too expensive?

It's cheap enough for every kind of drill bit you can find .Superior to chrome in every way.

-It would be more expensive than chrome because you would have to start with the stainless steel to do the Tin process.


I was thinking about entire barrels made of titanium.

There are titanium-framed revolvers and titanium knives... why not rifle barrels?
gdblair  [Member]
7/21/2008 8:24:36 PM EST

Originally Posted By Tolip:

Originally Posted By gdblair:

Originally Posted By Tolip:

Originally Posted By gdblair:
I'm waiting for someone to come out with a stainless bbl with titanium nitride bore.It would be slicker, more accurate , and more resistant to corrosion than chrome.



Why isn't titanium used more? Does it have unfavorable properties or is it just too expensive?

It's cheap enough for every kind of drill bit you can find .Superior to chrome in every way.

-It would be more expensive than chrome because you would have to start with the stainless steel to do the Tin process.


I was thinking about entire barrels made of titanium.

There are titanium-framed revolvers and titanium knives... why not rifle barrels?

I have a Taurus total titanium.They use a stainless liner in the bbl because titanium won't hold the rifling.It's a very elastic material and difficult machine. In the titanium nitride process it is put in a plasma state and permeates the top layer of the metal treated and adds less material than the chrome process thereby adhering to tolerances better.. Usually the the metal is stainless or chrome plated.Also, the Tin process does not flake.
joe-bananas  [Team Member]
7/21/2008 8:24:44 PM EST
Titanium is insanely expensive and very difficult to machine.
Keith_J  [Team Member]
7/21/2008 8:27:36 PM EST
Titanium nitride is a poor choice for the bore as the stresses tend to fracture it, resulting in more rapid erosion.

TiN coated drill bits are slicker for drilling gooey metals that ball up in the flutes when deep drilling. This coating is rapidly worn off the cutting edges so these bits have a similar life in that respect.

Chrome plated bores are much tougher and elastic, stretching with the applied stresses of the bore. It is also dense and resistant to atomic diffusion of the combustion gases like nitrogen and carbon. These elements will eventually diffuse into a plain steel/chrome moly barrel and leave the surface very brittle. Iron carbide (cementite) and iron-chromium nitridres are powerful hardening compounds, resulting in loss of elasticity. The higher level of chromium in stainless steel barrels lowers this formation as does the higher finish levels used on such materials.

Keith_J  [Team Member]
7/21/2008 8:31:29 PM EST
Titanium does not have the wear properties of good chrome moly/ stainless steels. In addition, it has a lower modulus of elasticity, meaning it will experience greater stress.

It also is quite reactive in the rifle barrel temperature range. When that propellent burns, it generates flame temperatures over 4000 F and a very rapid ramp-up. The temperature is also proportional to pressure, meaning the chamber and throat are most affected. The duration is longest there.
gdblair  [Member]
7/21/2008 8:34:46 PM EST

Originally Posted By Keith_J:
Titanium nitride is a poor choice for the bore as the stresses tend to fracture it, resulting in more rapid erosion.

TiN coated drill bits are slicker for drilling gooey metals that ball up in the flutes when deep drilling. This coating is rapidly worn off the cutting edges so these bits have a similar life in that respect.

Chrome plated bores are much tougher and elastic, stretching with the applied stresses of the bore. It is also dense and resistant to atomic diffusion of the combustion gases like nitrogen and carbon. These elements will eventually diffuse into a plain steel/chrome moly barrel and leave the surface very brittle. Iron carbide (cementite) and iron-chromium nitridres are powerful hardening compounds, resulting in loss of elasticity. The higher level of chromium in stainless steel barrels lowers this formation as does the higher finish levels used on such materials.


That is interesting.
Wouldn't copper be considered "gooey"?
-ETA- rifling tends to be more of a bearing surface than a cutting surface?
Keith_J  [Team Member]
7/21/2008 8:44:30 PM EST
Yes, copper is "gooey" but so are austentic stainless steels and some low carbon steels.

TiN lined bores would rapidly "crack" the coating surface as this material has very limited elasticity. The edges of these cracks would be focal points of erosion as well as increasing friction.

This same thing eventually happens to all unlined barrels, the surface steel becomes brittle from nitrogen and carbon diffusion along with the high temperatures.

Copper bullet jackets are actually a 5% Zn brass. At the high temperatures of the bore, the zinc boils off, shedding the copper as a fine dust and limiting its buildup. Pure copper jackets will rapidly foul a bore.
199  [Team Member]
7/21/2008 8:44:42 PM EST

Originally Posted By Keith_J:
... It is also dense and resistant to atomic diffusion of the combustion gases like nitrogen and carbon. ...

I always suspected that!
gdblair  [Member]
7/21/2008 8:45:01 PM EST

Originally Posted By Keith_J:
Titanium does not have the wear properties of good chrome moly/ stainless steels. In addition, it has a lower modulus of elasticity, meaning it will experience greater stress.

It also is quite reactive in the rifle barrel temperature range. When that propellent burns, it generates flame temperatures over 4000 F and a very rapid ramp-up. The temperature is also proportional to pressure, meaning the chamber and throat are most affected. The duration is longest there.


Titanium has a melting temp above 5000 f , that is why they use it in jet engines.
gdblair  [Member]
7/21/2008 8:46:24 PM EST

Originally Posted By 199:

Originally Posted By Keith_J:
... It is also dense and resistant to atomic diffusion of the combustion gases like nitrogen and carbon. ...

I always suspected that!

Then why does titanium stand up better in the human body than chrome?
Keith_J  [Team Member]
7/21/2008 8:47:54 PM EST

Originally Posted By gdblair:

Originally Posted By Keith_J:
Titanium does not have the wear properties of good chrome moly/ stainless steels. In addition, it has a lower modulus of elasticity, meaning it will experience greater stress.

It also is quite reactive in the rifle barrel temperature range. When that propellent burns, it generates flame temperatures over 4000 F and a very rapid ramp-up. The temperature is also proportional to pressure, meaning the chamber and throat are most affected. The duration is longest there.


Titanium has a melting temp above 5000 f , that is why they use it in jet engines.
Try more like 3000 F. And it is highly reactive to nitrogen, forming TiN. And carbon, oxygen...

I have made flame-thrower blanks using pistol powder and powdered titanium.
gdblair  [Member]
7/21/2008 8:49:32 PM EST

Originally Posted By Keith_J:
Yes, copper is "gooey" but so are austentic stainless steels and some low carbon steels.

TiN lined bores would rapidly "crack" the coating surface as this material has very limited elasticity. The edges of these cracks would be focal points of erosion as well as increasing friction.

This same thing eventually happens to all unlined barrels, the surface steel becomes brittle from nitrogen and carbon diffusion along with the high temperatures.

Copper bullet jackets are actually a 5% Zn brass. At the high temperatures of the bore, the zinc boils off, shedding the copper as a fine dust and limiting its buildup. Pure copper jackets will rapidly foul a bore.

If this is true , wouldn't the greater lubricity over chrome help the bore last longer?
Keith_J  [Team Member]
7/21/2008 8:50:08 PM EST

Originally Posted By gdblair:

Originally Posted By 199:

Originally Posted By Keith_J:
... It is also dense and resistant to atomic diffusion of the combustion gases like nitrogen and carbon. ...

I always suspected that!

Then why does titanium stand up better in the human body than chrome?


Titanium forms an oxide layer, much like aluminum, and this is highly biocompatible. Bone will adhere to this oxide layer. Chromium, which also forms an oxide layer that is protective, can be an irritant. And the nickel in stainless? Bad juju, hence most 300 stainless steel bioimplants are electropolished to remove surface Ni.

Keith_J  [Team Member]
7/21/2008 8:51:28 PM EST

Originally Posted By gdblair:

Originally Posted By Keith_J:
Yes, copper is "gooey" but so are austentic stainless steels and some low carbon steels.

TiN lined bores would rapidly "crack" the coating surface as this material has very limited elasticity. The edges of these cracks would be focal points of erosion as well as increasing friction.

This same thing eventually happens to all unlined barrels, the surface steel becomes brittle from nitrogen and carbon diffusion along with the high temperatures.

Copper bullet jackets are actually a 5% Zn brass. At the high temperatures of the bore, the zinc boils off, shedding the copper as a fine dust and limiting its buildup. Pure copper jackets will rapidly foul a bore.

If this is true , wouldn't the greater lubricity over chrome help the bore last longer?


For low stress barrels, yes. The combined stress of heat and pressure and the intense pressure gradient imposed by the bullet is too much for TiN coated barrels. Or Ti barrels alone.
gdblair  [Member]
7/21/2008 8:55:35 PM EST

Originally Posted By Keith_J:

Originally Posted By gdblair:

Originally Posted By Keith_J:
Yes, copper is "gooey" but so are austentic stainless steels and some low carbon steels.

TiN lined bores would rapidly "crack" the coating surface as this material has very limited elasticity. The edges of these cracks would be focal points of erosion as well as increasing friction.

This same thing eventually happens to all unlined barrels, the surface steel becomes brittle from nitrogen and carbon diffusion along with the high temperatures.

Copper bullet jackets are actually a 5% Zn brass. At the high temperatures of the bore, the zinc boils off, shedding the copper as a fine dust and limiting its buildup. Pure copper jackets will rapidly foul a bore.

If this is true , wouldn't the greater lubricity over chrome help the bore last longer?


For low stress barrels, yes. The combined stress of heat and pressure and the intense pressure gradient imposed by the bullet is too much for TiN coated barrels. Or Ti barrels alone.

Well, I've learned alot. Thanks!
gdblair  [Member]
7/21/2008 10:19:17 PM EST

Originally Posted By Keith_J:

Originally Posted By gdblair:

Originally Posted By Keith_J:
Titanium does not have the wear properties of good chrome moly/ stainless steels. In addition, it has a lower modulus of elasticity, meaning it will experience greater stress.

It also is quite reactive in the rifle barrel temperature range. When that propellent burns, it generates flame temperatures over 4000 F and a very rapid ramp-up. The temperature is also proportional to pressure, meaning the chamber and throat are most affected. The duration is longest there.


Titanium has a melting temp above 5000 f , that is why they use it in jet engines.
Try more like 3000 F. And it is highly reactive to nitrogen, forming TiN. And carbon, oxygen...

I have made flame-thrower blanks using pistol powder and powdered titanium.

I may be more closely describing Tin, it's melting point IS above 5200F.Also, a PVD process is being used on M1 Abrahms bbl's now to increase wear qualities above and beyond alloy steels+chrome.Ticn?
Keith_J  [Team Member]
7/21/2008 11:17:09 PM EST

Originally Posted By gdblair:

Originally Posted By Keith_J:

Originally Posted By gdblair:

Originally Posted By Keith_J:
Titanium does not have the wear properties of good chrome moly/ stainless steels. In addition, it has a lower modulus of elasticity, meaning it will experience greater stress.

It also is quite reactive in the rifle barrel temperature range. When that propellent burns, it generates flame temperatures over 4000 F and a very rapid ramp-up. The temperature is also proportional to pressure, meaning the chamber and throat are most affected. The duration is longest there.


Titanium has a melting temp above 5000 f , that is why they use it in jet engines.
Try more like 3000 F. And it is highly reactive to nitrogen, forming TiN. And carbon, oxygen...

I have made flame-thrower blanks using pistol powder and powdered titanium.

I may be more closely describing Tin, it's melting point IS above 5200F.Also, a PVD process is being used on M1 Abrahms bbl's now to increase wear qualities above and beyond alloy steels+chrome.Ticn?


Nitrides and carbides are very brittle materials. Think ceramic. Yes, high melting points and with the right process, they are compact and stable. On larger bores that can be prestressed by a process called autofrettage, the resultant compressive stress in the barrel can prevent elastic damage to such coatings. But there is always the issue of thermal stress in boundary layers.

A_Free_Man  [Member]
7/22/2008 6:17:53 AM EST
Getting back to the OP's question, SS barrels, I own all types.

Oly often substitutes SS for CM at no extra charge. And their M4 contour barrel is available only in SS last time I looked.

MOST of the accuracy of SS barrels is because they are generally bull barrel contours. SS is chosen for bull target barrels because it rifles nicely. But Oly is one of the few who make the more "normal" contours from SS. The difference in accuracy of barrels with similar contour, but SS, chromemoly (unlined) and chrome lined chromemoly all but disappears when you start shooting real rifles. There is just very little practical difference.

Durability? I have "rode hard and put away wet" SS barrels. In semiauto use, the barrel extension wears out before the bore does. I don't know how SS will do on full auto, but right now the local Sheriff's Office is trying its best to wear out one of my discarded SS barrels (20k+ rounds) on one of their M16's and not having much success.

Treat your SS barrel just as you would any other barrel.
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