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met·al·lur·gy
ˈmedlˌərjē/
noun
the branch of science and technology concerned with the properties of metals and their production and purification

in·vest·ment cast·ing
nountechnical
a technique for making small, accurate castings in refractory alloys using a mold formed around a pattern of wax or similar material which is then removed by melting

https://www.americanrifleman.org/articles/2014/9/24/casting-call-rugers-investment-casting-process


How can a "soup" of molten metal poured into a mold be strong enough to become a rifle action that must endure such high pressures?

Obviously the Ruger action holds up, but not understanding how it is done causes me to not have full confidence.

Can anybody put it in laymen's terms?

And to add to the confusion; how can/does Ruger make an investment casting stainless all that strong?

Last edited by Robert_White; 09/29/16.

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The "soup" which Ruger (and other companies) uses to form their products are dependent on alloys which differ significantly from the typical iron castings (or zinc, and other non-ferrous castings) we are accustomed to which are often inferior in strength for purposes such as guns.

Specialized metal castings are actually used a lot more commonly - not just investments- than we often realize. Investment casting just happens to allow more complex forms to be cast and done closer to final shape and size.


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Not sure if this is simple enough, but actually investment casting can produce parts that are stronger than forged. The reason is that if very precise and accurately controlled powdered metallurgy is used you end up with a finer grained structure than can be produced from billet. Also actions forged from billet originally started out as a casting.

It all comes down to the care and quality put into the part. You can have good castings and bad castings. You can start with a high quality billet and forge or machine a great part, or you can start with low grade crap billet and end up with the same in a finished part.

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Originally Posted by Robert_White
met·al·lur·gy
ˈmedlˌərjē/
noun
the branch of science and technology concerned with the properties of metals and their production and purification

in·vest·ment cast·ing
nountechnical
a technique for making small, accurate castings in refractory alloys using a mold formed around a pattern of wax or similar material which is then removed by melting

https://www.americanrifleman.org/articles/2014/9/24/casting-call-rugers-investment-casting-process


How can a "soup" of molten metal poured into a mold be strong enough to become a rifle action that must endure such high pressures?

Obviously the Ruger action holds up, but not understanding how it is done causes me to not have full confidence.

Can anybody put it in laymen's terms?

And to add to the confusion; how can/does Ruger make an investment casting stainless all that strong?


It's not pot metal, the "soup" is 4140 steel in the case of chrome moly.

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So it is all about the "fine grain" ?

How much stress does the actual action endure in a bolt action rifle? The end of the barrel forms most of the actual chamber. The bolt lugs lock into the action so the force is mostly to shear off backwards?

Am I thinking rightly?

By contrast the Remington 700 is machined from billet? But the billet was hammer forged? To straighten the grain???

Last edited by Robert_White; 09/29/16.

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Originally Posted by 458 Lott
Not sure if this is simple enough, but actually investment casting can produce parts that are stronger than forged. The reason is that if very precise and accurately controlled powdered metallurgy is used you end up with a finer grained structure than can be produced from billet. Also actions forged from billet originally started out as a casting.

It all comes down to the care and quality put into the part. You can have good castings and bad castings. You can start with a high quality billet and forge or machine a great part, or you can start with low grade crap billet and end up with the same in a finished part.


Aren't you mixing two concepts here?

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The Model 700 action has a much simpler shape than a Ruger 77. When the 700 was developed it was designed around being able to easily machine it from simple round bar stock. The machining operations necessary to mill a 77 from a billet would have driven the price much higher when it was developed.

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There is also the matter of heat treatment involved in both the 700 and 77 actions. "Pot" metal castings aren't typically heat treated, nor would they respond to it the same.

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"How can a "soup" of molten metal poured into a mold be strong enough to become a rifle action that must endure such high pressures?"

A billet was once a molten soup. Check out some pictures of blast furnaces, open hearths and steelmaking. Lots of hot soup there.

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Originally Posted by Gringo Loco
There is also the matter of heat treatment involved in both the 700 and 77 actions. "Pot" metal castings aren't typically heat treated, nor would they respond to it the same.


yep heat treatment not done right for either of those two would result into ugly instances. you can't look at investment casting done by Ruger and think "Dutch Oven" results.


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I can remember reading the same questions and answers 40+ years ago...


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The point of casting is to have an efficient way of making complex shapes, that are either impossible or cost prohibitive to forge. And forging dies - hard tooling - take a lot of abuse and tend to be relatively expensive. Casting patterns can generally be relatively low-strength, inexpensive materials.

Good castings will be clean and dense - not a lot of impurities in the metal, nor voids (air bubbles) that formed when the metal was liquid. Impurities can act as stress raisers, and cause premature failure of the part. Voids are an obvious problem.

Firearms receivers are generally designed to have good strength, but also good toughness, not brittle. A brittle part could shatter with an unexpected stress, like an overload, and be very dangerous to the shooter.

Good forgings will usually have better ultimate strength and toughness, but a Mauser-style receiver was designed in the days of weaker steels; a good casting is plenty strong enough. In higher-stressed, really critical parts, like barrels, you will still see forgings, and bar stock production.

Aside from clean, void-free metal, a good steel casting will then depend on a good heat treatment. In that operation the grain size and strength/hardness can all be refined to give the desired properties.


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Originally Posted by 5thShock
A billet was once a molten soup. Check out some pictures of blast furnaces, open hearths and steelmaking. Lots of hot soup there.


That was my first thought....steel always starts out as soup before it is shaped into something!


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According to a Brian Pearce article on 77s, the Ruger castings actually tested as stronger than the bar stock that many other actions are machined from. Supposedly, the bar stock can shear along certain internal stress lines if memory serves.

MIM parts, on the other hand, aren't as dense as other steels (95% if I recall correctly). Kahr economy model autos feature MIM takedown levers that are somewhat larger than the machined ones on the high-end guns. The MIM rear sight on a Kimber Target II my son owned sheared off at the top of the dovetail just from recoil stress.


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As long as the material being poured is hot enough to go into solution before cooling and is properly heat treated and tempered for the specs. required it will work fine. Forging is used to shape steel but in practical terms does not induce magical properties into the steel above and beyond other methods of shaping steel, contrary to popular opinion.

Last edited by SBTCO; 09/29/16.

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I have a question; why do some of the older Ruger 77 receivers turn "plum/purple" as they age?

I have a 77R in 6.5 Rem Mag that is very "plum", while the barrel is still dark blue. I assume that they were blued at the same time and the receiver has turned color, while the barrel has remained dark blue, because of the alloy used.

I don't see any of the newer Ruger 77s turning plum color, or maybe I'm just not looking hard enough to see them.

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Link: https://www.amazon.com/Materials-Processes-Manufacturing-Paul-DeGarmo/dp/047136679X

Taught this curiculum once,...GTC 105 / GTC 206 at a local CC, included in their 2 years associate degree tech program.

I DON"T advise buying anything newer than the 8th edition,...they "reprinted" with many errors, and deletion of material that should have been kept .

Just a GREAT book to have around when a bunch of young'uns start asking questions

Chapters 13, through 19 were my favorites,...covering casting, forging, rolling, extruding, etc.

Can't recommend this book highly enough, for those who take interest in threads of this nature.

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Originally Posted by SBTCO
As long as the material being poured is hot enough to go into solution before cooling and is properly heat treated and tempered for the specs. required it will work fine. Forging is used to shape steel but in practical terms does not induce magical properties into the steel above and beyond other methods of shaping steel, contrary to popular opinion.


Sorry, ....WRONG.

Etched Photo-micrographs will show superior grain structures in properly designed forgings AND castings that will not be present in the identical piece machined from rolled or cast billet.

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Originally Posted by 260Remguy
I have a question; why do some of the older Ruger 77 receivers turn "plum/purple" as they age?

I have a 77R in 6.5 Rem Mag that is very "plum", while the barrel is still dark blue. I assume that they were blued at the same time and the receiver has turned color, while the barrel has remained dark blue, because of the alloy used.

I don't see any of the newer Ruger 77s turning plum color, or maybe I'm just not looking hard enough to see them.


Don't know, but the receiver on the little refinished Savage .410 I bought yesterday is kinda purple. I've also seen that color on the bolt release housing on a Garcia Sako .223 I used to own.


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Originally Posted by 260Remguy
I have a question; why do some of the older Ruger 77 receivers turn "plum/purple" as they age?

I have a 77R in 6.5 Rem Mag that is very "plum", while the barrel is still dark blue. I assume that they were blued at the same time and the receiver has turned color, while the barrel has remained dark blue, because of the alloy used.

I don't see any of the newer Ruger 77s turning plum color, or maybe I'm just not looking hard enough to see them.


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