Very Best Materials For Components

[JasonT]

Hey there folks!

So I was having a bit of a think and stretching my brain's legs about the ideal materials for manufacture of various rifle components. I come from an engineering background with some machining thrown in, but I'm by no means an expert.

Action Body: 300M? 4140? S7?

Bolt: 300M? 4340? Both allow high hardness and toughness

Barrel: 4150? 416R? 17-4?

Any other ideas?

 

[nicholst55]

The Army specifies 4150 for machine gun and rifle (think M4 Carbine and M16) barrels due to the amount of heat they experience. Then they hedge their bet by chrome lining them, so they resist corrosion better.

 

[Texas10]

Back in the day when I was building ASROC (anti submarine rocket) boosters out of 4340, we rolled sheet material into tubes and seam welded them. Forgings were welded onto the tubes, machined and then the assembly was heat treated. These were essentially 11.65 inch dia solid fuel rockets.

You would not believe how hard and tough that material would become after heat treat. We pressure tested them to 2000 psi hydraulically, while mounted upright on a test fixture. One day the tech forgot to let all the air out while filling one for test, creating the biggest water rocket you ever saw.

At 2000 psi it stripped off the retainer nut and launched the rocket 30 ft into the air, coming down and bouncing up and down on the concrete floor like a super ball.

After all that, there wasn't so much as a scratch or dent on it. Lot's of witness marks on the concrete floor where it bounced, but NOTHING touched that 4340 hardened steel.

I've often wondered what would happen if you took that plain jane 4130 barrel and heat treated to a much higher level of hardness/toughness. Harmonics would definitely change, probably last forever too. But the ringing sound it would make while being shot would be a dead giveaway that you were shooting something special.

 

[ireload2]

Materials cost money to buy and process.
There are always budget limitations.
I have worked in aerospace, semiconductor and medical implant industries.
Corrosion resistance, fatigue resistance and strength are requirements of all of these product types.

There are upper division engineering texts that provide many methods to classify and quantify the selection of engineering materials. My materials selection text was written by Michael F Ashby. Check one out at your library. You will be amazed that for the most part the best trade offs in cost vs performance have already been picked.
Actions could probably be improved dimensionally by using prehardened steel so there is no warpage due to heat treatment.

Some of the materials you mentioned are very good for some application and are terrible for others. Take 17-4 PH for example. It makes excellent static components. But if you use it for sliding or rotating components it become a very easy galling material when ran against other 17-4 PH parts. I call it gallomatic.... Make a Browning A5 or a machinegun action out if it and you would be lucky to get 100 rounds without galling.

I will also mention that the US govt considers some materials as strategic because of their rarity and importance. Those materials are discouraged for new designs because of the impact on production in national emergencies or shortages due to geopolitical events.

Hey there folks!

So I was having a bit of a think and stretching my brain's legs about the ideal materials for manufacture of various rifle components. I come from an engineering background with some machining thrown in, but I'm by no means an expert.

Action Body: 300M? 4140? S7?

Bolt: 300M? 4340? Both allow high hardness and toughness

Barrel: 4150? 416R? 17-4?

Any other ideas?

 

[SteveOak]

Back in the day when I was building ASROC (anti submarine rocket) boosters out of 4340

I have been up close and personal with an ASROC.

I don't have anything to contribute to improve the list of optimum materials but I do have a story of why stainless is used for barrels.

I hung out a bit in the shop of a barrel maker, a name you would recognize. I asked him why stainless was used for barrels. He smiled and said, they shine up nice so they look pretty, it is softer and easier to cut than chrome moly and it wears out quicker so they buy a replacement sooner.

 

[Hydenseek]

Interesting...

 

[retired]

not corrosion...errosion

The Army specifies 4150 for machine gun and rifle (think M4 Carbine and M16) barrels due to the amount of heat they experience. Then they hedge their bet by chrome lining them, so they resist corrosion better.

 

[retired]

very true....

I have been up close and personal with an ASROC.

I don't have anything to contribute to improve the list of optimum materials but I do have a story of why stainless is used for barrels.

I hung out a bit in the shop of a barrel maker, a name you would recognize. I asked him why stainless was used for barrels. He smiled and said, they shine up nice so they look pretty, it is softer and easier to cut than chrome moly and it wears out quicker so they buy a replacement sooner.

 

[KMart]

The Army specifies 4150 for machine gun and rifle (think M4 Carbine and M16) barrels due to the amount of heat they experience. Then they hedge their bet by chrome lining them, so they resist corrosion better.

http://www.dtic.mil/dtic/tr/fulltext/u2/a953117.pdf



The survey team concluded that the major problem was deterioration of rifle barrels caused by chamber pitting and the accumulation of copper fouling. It estimated that approximately 10 percent of the Ml6's in Vietnam would require a barrel replacement every three months. To reduce the rate of barrel deterioration, the team recommended speeding up deliveries of the recently adopted improved lubricant 0UL-L-46000A) LSA and chrome plating the rifle chambers.