Barrel steel, beyond stainless

[davidjoe]

I have lined up with conventional thinking, always using stainless barrels for matches. Target rifles get wet from time to time after all, and they do cost more, so they must be better.

Lately though, I have contemplated the proportion of elements that make stainless steel more resistant to rust. I have looked at my collection of buttons, stubs, and throats and threads. Though we are kind of conditioned to consider stainless “tougher,” things like smearing, galling and how the softer metallic elements are also the rust resistant ones that may be used, come to mind.

Then, when I consider every cost-is-no-object barrel, whether to endure sea spray and mist, scorching heat, or, closer to our purposes, military procured precision fire small arms, always having one additional digit in its price, I just don’t see stainless steel being chosen.

Surely, at these highest, most demanding levels of uses, stainless is not too expensive to select. An F-22 ($180M) has a rotary cannon with rifled barrels, to engage another $100M target. While I want to think my shots into the berm matter (2 dollars), those shots actually do. So I guess my question is why haven’t entities like ATK, GE, FNH, SACO Defense and all, come around?

Assuming a willingness to coat, (at least with oil) should we try CM? Could it last less long?

 

[jelenko]

So, I've wondered about this very question - a lot.
On Lija's website, they say that CM is more resistant to abrasion and SS is more resistant to heat erosion.
They don't say, but my understanding is there is no difference in inherent accuracy between the two metals. Apparently SS can be machined more precisely => better chance of being more accurate.

 

[MClark]

It’s a trade off between barrel life and being able to rifle the bore.

 

[DHall_37]

I’m in a materials class and my uncle is an engineer so maybe I can weigh in.

stainless steels like 4140, nickel chromium steels and high carbon steels are incredibly strong for their price, weight and can be machined easily they are also very weather resistant. My professor said that more chromium adds more weather resistance. Nickel, carbon and a few other elements add durability.

issues like in Vietnam when barrels were rusting out was because they weren’t chrome lined. Army probably went cheap with their steel and extra cheap with no lining. I’m not sure if modern barrels are lined or not.

A softer rust resistant metal like aluminum is a No go for a barrel. I believe that the metal will start to flex, budge and crack as a 60,000 psi round is probably pushing the elastic region on that metal quite a bit.

Edit: one thing I forgot to add was that tool steels like HSS and tungsten carbide will not make a cost efficient barrel. It will be probably $10,000+. My uncle said that titanium can become brittle, potentially enduce faster fire cracking in a bore. Titanium also likes to work harden unless special coolant and constant feed rates are being used. Then you’ll have to rifle it with what? A HSS button? That’s not gonna work, the barrel will eat that button for breakfast.

Sorry if this sound like a rant, I’ve been thinking about barrel steels a lot recently too.

 

[wkdickinson]

FWTW - a long time ago I asked Boots Obermeyer "what is the difference" between SS and CM barrels". He told me that CM accuracy started to degrade with the first bullet and continued until..., where SS stayed at the same level of accuracy "until it didn't". He went on to say that could and often did, happen right in the middle a match.

 

[davidjoe]

It’s a trade off between barrel life and being able to rifle the bore.

I need some cooler powders and softer copper jackets.

 

[gunsandgunsmithing]

Machineability and costs are surely major factors but I suspect things as simple as the mil-spec manganese phosphate parkerizing that's on just about all things military, may also play a role. One thing is certain, you should never try to rationalize government actions. It'll drive ya crazy.

 

[Ned Ludd]

Avoid a barrel that is rusted and has a rat's nest in it like the one pictured.

I think the real question here is what happens in the throat. How many times have you "shot out" a barrel where the first 2 to 4 inches of barrel exhibited major land erosion and fire-cracking, but the last two feet or so looked almost brand new? An "ideal" barrel steel would largely mitigate what happens over time primarily in the throat region. The question, is that really feasible? No matter what powder and bullet weight you choose, a lot of heat and pressure is generated in that region of the barrel. The notion of using a type of steel that is more resistant to heat and pressure is all well and good, but if the increased price of such a barrel isn't directly proportional to the increase in barrel life, you're better off buying two SS barrels, instead.

 

[liljoe]

Bartlein has a new material available. Call them up and talk to them about it.
Joe

 

[davidjoe]

Bartlein has a new material available. Call them up and talk to them about it.
Joe

Yes, they are fellow shooters, envelope expanders, and great to talk to. I have a lot of appreciation for their gain twist abilities, and between that, 5-R, extra length and upgraded steel options, they really do put the custom in barrels.

I’m a twice-monthly string-fire barrel abuser. I love them, but it seems our F-Class matches were devised by the barrel makers themselves. Shoot long strings fast, make the targets small enough that the barrels need to be perfect, make the gear heavy enough that the process is painless, and that all assures the 80% still-good take off’s are too big and silly to find a home on sporters.

I’m too old now to appreciate smoking the tires, now I’m looking for the ones that go 80,000 miles.

 

[3Sigma]

Everything is a trade off. Especially on "plowed ground" such as this. You fix one issue and you find three more problems.

You have to decide what attributes are most important and go from there.

High alloy hardened steel is very wear resistant, but extremely difficult to gun drill, rifle, and chamber (possibly requiring carbide reamers) Annealed/unconditioned steel is easier, but warps like mad once heated, quenched, and tempered.

Hammer forging is a possible answer (and is how this process came about), but it lacks precision of a cut or buttoned barrel and has a risk of residual stresses impacting performance.

All this to say 400 series SST is pretty good for the role. Chrome moly (41xx/43xx) is pretty good as well. You have to move to some pretty exotic alloys to make a significant improvement in most areas, and it will take some deep pockets to even get a mill to run a batch to spec (you probably have to buy a whole heat).

 

[357Mag]

I need some cooler powders and softer copper jackets.

Davidjoe -

Howdy !

Barrel life and maintenance in military applications are a different thing than 'civie use.

All branches of the U.S. Armed Services are non-profit. The cost money to train,equip, sustain; etc.
The one place within the military where they can make some money back for the Gummint' is
" AMARC "...... the aircraft " boneyard " out @ Davis-Monthan AFB in Tucson, AZ. AMARC on occasion
pulls aircraft from storage, refurbishes them, and prepares for flight. Sometimes for foreign governments, and that's where the profit can come from.

As regards barrels on things like fighter jets and A-10s:
Scheduled and non-scheduled maintenance and cleaning is arranged to provide useful barrel life and accuracy. When time comes for replacement, the barrels get replaced. Cost at the user-level is seldom the issue. Example: if the Vulcan canon on a fighter needs a barrel or barrels replaced, it will get them. Stuff like that is seldom defered, because most of the time.... the $$$ has been alocated for it. The funding behind such efforts makes it all possible.

In the 37 yr I was in the military, it wasn't until year 35 that I was first asked to control or limit supply requisitions for my Aircraft Maintenance repair shop. The money was always " there ", and not often were budgets " tight ". It was quality first... fly when you have the plane " fully mission capable " ) or " FMC ".
For military war machines that shoot at things, drops bombs and such..... being FMC is where it's at.


With regards,
357Mag

 

[davidjoe]

That 105 mm main gun barrel on the static display Abrams struck me as the best steel I’ve ever seen or felt, or rapped on. The rifled 105 gun was replaced by the German 120 mm smoothbore from the Leopards, a long time ago, and that particular tank looked as if it could have sat there since the birth of current recruits. It wasn’t stainless steel, yet most of it where bare barely acquired a relatively superficial orange hued film, if anything.

The density of that steel reminded me of the strongest forged wrenches you can buy, or the shanks of $400 pad locks. Items that you just don’t forget or confuse with the mundane. I had the distinct impression that the steel in that cannon barrel was the highest strength and most expensive steel of any large object I had seen before, fully commensurate with the rest of the $4M vehicle.

 

[M60A3TTS]

Tank guns are chrome lined and use soft copper, aluminium or even plastic obturator rings. The M900 APFSDS round for the 105 M68A1 gun, that it was authorized for use in, late model M60a3, and M1 and M1IP tanks was rated at 4800 FPS. M829 A3-4 series rounds fro the M256 and M256A1 smoothbore guns are rated at almost 5900 FPS at the muzzle.

Barrel life is measure in EFCs, effective full power cartridge, nominal 1500 rds. for the M256 series guns. Many were replaced long before and long after, the specified intervals. Depended on the condition of the bore.

Some rounds such as the M836 and A1 version rated 1, meaning one round effective wear. Training rds, M856 and the 830, I think ,I remember were rated at .5 meaning 1/2 of one rd wear. The M829 A3 and 4 really thumped and were rated at 2. The M1A1 and later variants, smoothbore guns were to be replaced if 18 inches or more in any one area of bore had the chrome stripped out. If close to the bore , 6 inches, and if at the muzzle none. Over the years this changed back and forth depending on ammo and use, training or combat. Accuracy was somewhat uneven, as some barrels, in what seemed to be poor shape, shot cloverleafs at 1200 m, and better bores produce 3ft groups. Also could have been crew or FC issues.

The propellant has antiflash, which you wouldn't believe if you saw them fire at night, anti corrosion ,and temp moderating additives. Ordnance steels are crazy stuff, I wasn't a Master Gunner , so I don't know exactly, the alloy used.

It's been 20 years since I last crewed an M1 and 26 since the 60's went out of service. You never forget your first girl. Good times.

 

[JMA]

A friend of mine had gone a tour off Watervliet Arsenal where artillery barrels are made.
He was told they are made of an alloy that is not commercially available and when they barrels are taken out of service they are recycled.

 

[PRR1957]

Machineability and costs are surely major factors but I suspect things as simple as the mil-spec manganese phosphate parkerizing that's on just about all things military, may also play a role. One thing is certain, you should never try to rationalize government actions. It'll drive ya crazy.

Manganese Phosphate should only be applied to the outside of a firearm barrel as it requires the metal to be media blasted, usually with silica oxide, in order for the oxide finish to adhere properly. This metal oxide finish should not be done to the chamber and bore of a firearm barrel as it would ruff/score the surface and cause extreme problems with cartridge chambering/extraction and copper jacket fouling of the rifled bore. Any surface that didn’t need this oxide finish would be covered in thick high adhesive tape or blocked off with silicone plugs for the media blasting process prior to the parkerizing. I used to work for a company that applied this type of metal finish.

 

[gunsandgunsmithing]

Manganese Phosphate should only be applied to the outside of a firearm barrel as it requires the metal to be media blasted, usually with silica oxide, in order for the oxide finish to adhere properly. This metal oxide finish should be done to the chamber and bore of a firearm barrel as it would ruff/score the surface and cause extreme problems with cartridge chambering/extraction and copper jacket fouling of the rifled bore. Any surface that didn’t need this oxide finish would be covered in thick high adhesive tape or blocked off with silicone plugs for the media blasting process prior to the parkerizing. I used to work for a company that applied this type of metal finish.

Agreed

 

[CharlieNC]

What about the Lothar Walther barrels which are reportedly harder and more difficult to machine? Any better useful life?

 

[davidjoe]

A friend of mine had gone a tour off Watervliet Arsenal where artillery barrels are made.
He was told they are made of an alloy that is not commercially available and when they barrels are taken out of service they are recycled.

Ahh, after my encounter with that barrel I photographed, I can see both those points being 100% the case. I have never seen steel like that before, and I have experienced my share.

I’d love to know the “recipe” of that alloy. They manage to rifle it.

 

[davidjoe]

What about the Lothar Walther barrels which are reportedly harder and more difficult to machine? Any better useful life?

Those barrels, the way I wanted two, were not at all easy to get, at least when I tried.