I'm interested in the science/engineering of firearms, automobiles, aero etc in general like a lot of us are and always looking for the next best thing to "make it better."   I watched some YouTube videos of people torture testing their AR's and AK's and the only gun I saw survive the test of 2,300+ rounds of full auto was the POF P416 from Iraqveteran8888.  It seemed in those videos the barrel was the weakest link and heat was the culprit.  Also, the links of Battlefield Las Vegas here at this forum on reading about guns with 200,000 rounds fired through them got me thinking on ways to increase the lifespan and longevity of firearms that are put through extreme abuse.

I Googled up "Heat resistant steel alloys" and first link I saw this...
https://www.hpalloy.com/Alloys/hightemperature.aspx

HASTELLOY ® Alloy X (HX)
(UNS N06002) Ni 47.5, Cr 21.8, Fe 18.5, Mo 9.0
"Excellent high temperature strength and oxidation resistance to 2200°F. Excellent forming and welding characteristics. Resistance to oxidizing, reducing, and neutral atmospheres. Resistant to SCC in petrochemical applications. Good ductility after prolonged service temperatures of 1200, through 1600°F for 16,000 hours. Gas turbine combustion cans and ducting, heat-treating equipment, spray bars, flame holders, furnace rolls, furnace baffles, and flash drier components."

Hastelloy X is a nickel-chromium-iron-molybdenum superalloy with outstanding high temperature strength, oxidation resistance, and fabricability. Alloy X’s oxidation resistance is excellent up to 2200° F...
http://megamex.com/hastelloy_x.htm

Could that some day be used in firearms like barrels for fully automatic fire for prolonged periods of time?

Also, your opinions on lithium alloys 2055 and 2099 for receivers compared to 7075 T6.

Inconel is exceptional for use in high pressure, high temp (absolute temp and temp delta) applications...but it's pricey and a massive pain to work with.

you also need machinabilty
some alloys tend to chip more

i think this is why 416r was created

oh and harness, as well as other properties

its a balancing game

Here is Hastelloy X in pipe and tube form which got me thinking about gun barrels...
https://www.stindia.com/hastelloy-x-pipe-tubing-supplier.html

The Hastelloy X isn't inconel, it's in a different category called Hastelloy...
https://www.stindia.com/hastelloy-x-pipe-tubing-supplier.html

People shouldn't try to "make things better" without understanding how to match materials science and manufacturing processes with the intended application.

Aside from that is there really a "need" to have an infantry carbine/rifle that can withstand 2,000+ rounds of continuous automatic fire when a standard combat loadout is 7ish magazines to be fired semi? Those guys aren't doing any "test", they're creating clickbait YouTube content to get money and views.

Edit: No real advantage to Al-Li receivers aside from being a lighter and more expensive. Receivers don't actually do much besides hold the FCG and barrel really.

its possible its been tested
a quick google found this from the 70's

https://apps.dtic.mil/dtic/tr/fulltext/u2/751864.pdf

might be more out there

Heat is only one aspect. The ability to safely contain high pressure and resist abrasive wear are some others.

The cost of such a barrel would far exceed the benefit.  If the Army looked at it in 46 years ago, and one one has heard of it since, there might be a reason for that...

As to going away from aluminum...

Aluminum is the most common metal in the Earth's crust, and it is second only to steel in cost per pound.  No reason to change.

I work with all those steel alloys,  and I'd say 416 i's probably the best.  Inconel i's tough... reeal tough, . We use incolnel 939, and it's like working with diamonds. Also x45, ecy768. I believe thes a reason those super alloys aren't used

How much would an AR 15 barrel cost if it was made out of Hastelloy if you could put a price tag on it in dollars?

There’s a number of barrels made of 17-4 PH these days. While not Hastelloy, it’s still much tougher than 416R while still machining well.

. . . and there is a reason that liners stop about half way down the barrel . . .

Maraging C300 steel is the new rage in the suppressor game. I have no idea what its machinability is like, and I'm pretty sure it ain't cheap, but possibly more cost effective than Stellite/Inconel.

Lets just say hypothetically that the U.S. Dept of Defense wanted to create a barrel for AR 15s out of Hastelloy, even just a one off experiment, would that barrel made out of that material be effective in durability, strength, heat resistance for fully auto fire?  Would it be able to withstand the abuse everyday at Battlefield Las Vegas for over 100,000 rounds on a single barrel?

I asked the D.Eng/PE in the office next to mine and he said to contact him for rates to find out. I can also get a quote for manufacturing if you let me know if you'll be providing the material or if we'll have to source it ourselves.

You'll have to source it yourselves.  So how much will it cost?

An actual quote is going to cost you $200 which will be deducted from your invoice if you award a purchase order. Also you'll be required to pay for the material up front as well as 50% of manufacturing costs with the remainder due prior to delivery. PM me your manufacturing specifications and what if any engineering services you may require if you're serious and I'll work up an itemized  quote (material, manufacturing, engineering consultation).

Noveske did a few of those back in the day. I kick myself for not getting one. He basically said it wasnt worth the time-money and never did anymore. I read a claim that some guy had over 20k mostly f-a that still was not shot out.

The bottom line its not worth the cost to make a super barrel when replacements are so cheap.

Lets be honest less that 1% of the shooting population will wear out a barrel anyways.

I have no idea since my question above was a hypothetical.  How much would it cost to manufacture one 14.5 inch AR 15 barrel out of Hastelloy and how much to sell it for?

https://www.youtube.com/watch?v=XY8iNt064sE

I think to do it “economically” (lol) in any quantity greater than a few would need to be hammer forged. That or figure out how to EDM the bore and most of the rifling grooves before final polishing. Even then, chambering would be no fun. Inconel and hastalloy are difficult as hell to machine.

@Tigwelder1971

The stellite liner in the M60 barrels (which is the only one I'm familiar with) terminated about a quarter of the way down (a few inches forward of the chamber). This was done to lower cost (compared to a theoretical 100% stellite barrel).

Stellite is extremely difficult (aka expensive) to machine, and the liner only serves to slow throat erosion (which is what kills GPMG barrels first, unless someone dumps a ridiculous amount of heat into it via an extreme firing schedule).

The Battlefield Las Vegas threads got me interested in this.  Gun ranges are a great place to research reliability of guns, maintenance schedules etc, especially if the owner posts the reports from the armorers working there.

I think what the military should do is right before they release a new gun to the soldiers is they should send it to Battlefield Las Vegas and let the customers shoot the heck out of it to see how durable it is, use gun ranges with high round counts as a gauge and point of reference.

Build me a barrel that will take 3200 fps rounds in 6mm for 100,000 rounds and cost become a non issue.

Now we're talking.  But, are you referring to fully automatic for 100,000 rounds?  Now that's pushing the boundaries.

What's the best way to get the AR 15 up to a machine gun status and go toe to toe with a squad automatic?

Add a belt feed to it. Machine guns just can't have their magazines switched fast enough for a magazine to be a viable feed option, you need belt-fed ammo for machine guns.

I dunno, but finding out takes time and we don't work for free.

How old are you? Apparently you have no concept of how weapons are procured or how to value other people's time. Sounds like a teenager's mental masturbations to me...

...

As a machinist I’d say about 4 X the price of a single Hastelloy barrel after you scrapped the first 3

Nickel-based superalloys are extremely expensive.  They are also difficult to machine due to the high nickel content.

If money was no object, between Hastelloy or Inconel which would be more ideal for building a rifle barrel out of for longevity under extreme operating conditions like full auto?  Or, between the two, which one would wear out or fail first?

If you're comparing it to an M249 SAW (or MK46) and want that level of sustained-fire performance...


This is the only way that I know of, but now it's way heavier than the M249.

The Beta C mag is also a questionable feed system. They must be kept meticulously clean, and also lubed with graphite (or something).

Everything in small arms design is a compromise.
If you want to keep the weight down, you'll need something less capable than a water-cooled M16.

The M4A1 SOCOM is a good compromise for a lightweight general purpose full-auto weapon that's still a carbine (handles a little worse than the old M4A1 due to increased barrel weight), but now it'll tolerate ~14 30rd mags dumped back-to-back, as opposed to only ~8 for the original M4 profile barrel.

It cannot compete with a SAW for sustained fire however. No way.

It's fine for breaking contact and emergency FPF. That's all it has to do. It isn't a LMG.

Look at what Colt did with their older LMG...


This is a realistic compromise of overall weight vs a heavier barrel and thicker gas tube to soak up the heat better.

The newer Colt IAR is a different school of thought. Its design is focused on dissipating heat using an aluminum heat sink clamped to the barrel.


It also weighs a few pounds less than the old Colt LMG (so it handles a bit more like a standard infantry rifle).

You'd have to add lube to either of these during extended firing sessions, because it would cook off after a while, as the BCG starts to become dry, caked, and the friction increases.

That's where piston systems like the M27 IAR come in. The piston gives you a little more time with a cooler, cleaner, and lubricated BCG. That also comes at a cost of weight and increased mechanical complexity.

None of these systems give you M249 performance however. The SAW has plenty of barrel mass to take the heat, a big steel receiver to dissipate some heat, and large parts which are very likely to still perform when caked with carbon from firing.

It also is not a repurposed infantry rifle. It was designed from the ground up to provide significant sustained fire as an air-cooled weapon, and it's heavy (although a MK46 is less than 3 pounds heavier than the Colt LMG).

Check out KAC's 8.6 pound LAMG if you really want to see some lightweight belt-fed awesomeness.

KitBuilder, thanks for the reply.

That's what I was getting at, in order to ever get an AR 15 platform up to the level of a squad automatic will it require super alloys for the receiver and barrel?  Pushing the boundaries of the AR platform to new heights.

I think HK and POF are on the right track with their short stroke systems.  I think both HK and POF's 416 systems are the way of the future and will only get better over time but the short stroke system in AR's needs more time to mature and evolve (Pat Rogers said that in the carbine course thread).  But I think the materials/alloys will need to be stronger and more expensive.  The U.S. military thought there was more upside in going with a short stroke over a DI but that doesn't get to the bottom of reliability when barrels and receivers crack and break due to heat.

Even high grade greases will probably be needed or should have been used years ago instead of CLP...
Superior Industries - Tungsten Disulfide Grease Lubra Plex 4000...
https://www.superior-industries.com/lubra_plex_4000_product_269.html

The KAC LAMG looks awesome.

I also like the idea of the FightLite MCR Belt Fed AR15 where you can change out the upper receiver from a regular magazine fed AR to a belt fed AR like what MAC tested...
https://www.youtube.com/watch?v=d_QRcZnr4n4

At 12:55 in the video above MAC talks about one of the possibilities for their being a problem if that gun was used for the military is that it fires from a closed bolt and could lead to cook off.

Actually, the reason they are not full length is not purely cost related, think of the cost to interference fit a liner to a barrel tube and keep the liner perfectly concentric to the the barrel tube, have the rifling line up perfectly, and there cannot be a step at the internal mating of the liner bore to the barrel tube bore.  A full length liner would be much cheaper to assemble.  In fact, the first experimental Caliber .50 lined barrels were full length.  However, they found shrink fitting full length small arms barrel liners problematic (although, that is the way a 16 inch gun barrels).  By the 1970's these limitations were eliminated by advances in technology and new heat resistant materials caused the Army to revisit full length linings.

Most all of these materials proved that they were far better than traditional barrel steel at resisting the throat erosion, but all suffered muzzle wear that was as bad or worse that traditional steel.

Lol, brass balls and a drill press