Cast vs Forged

[mooreshawnm]

Can someone explain to me the difference between cast and forged receivers...had ARs in mind. Can't seem to find this via forum search and now I feel really foolish for asking a question everybody else undoubtably know the answer to.

Shawn

 

[joshua]

Difference between forged versus cast irons.

The forging process, a solid metal block is beaten into the desired shape. Forgings have a higher density compared to cast parts due to the pounding/compressing of steel.

Casting is a process where molten metal is poured into a mold to create the desired part. The molecular structure is not as dense so the integrity is not as strong as forged parts. Casting is cheaper than forging because it is faster to create a cast rather than hammer a piece of steel into shape. I have seen cast parts get brittle when hard chromed, I know because it happened to my frame. I'm hearing MIM is better than cast because the molten steel is sort of compressed in the cast I hope that helps some. josh

 

[mxwelch]

I'm a machinist and forging is the way to go as Joshua pointed out. Casting are nothing more than recycled material melted down and poured into whatever shape desired. I machined some parts one time and hit several ball bearings that didn't quite melt like the cheap iron around it.

When looking for an AR receiver go with the 7075 Aluminum, stay away from the 6061. The 7075 is harder and stronger.

 

[mete]

Joshua, forged material is NOT denser. There really isn't any difference between a forged and machined receiver such as a Rem 700 and a high quality investment cast one like the Ruger 77.....Just about all steel is from recycled material regardless of the type !!..Beside , metals don't have molecules !!! only crystals , that's why they're metals .History Channel had an excellent program about making a Ferrari.The engine is cast aluminum. For a car worth over $ 1 million you bet it's as high quality as is possible and it must be to withstand the high forces .

 

[cheygriz]

Forging and machining are the "old school" labor intensive past. Casting is the mass production future. it really is that simple.

Properly forged and CNC machined receivers are a thing of beauty, but labor intensive, and inordinately expensive.

Investment casting gives you a receiver that is just as strong, just as durable, and not really very pretty, but at half the cost.

With the prohibitive cost of union labor in this country, in a few decades, forged, machined weapons will be the province of the very rich only.

 

[mxwelch]

Forging and machining are the "old school" labor intensive past. Casting is the mass production future. it really is that simple.

Properly forged and CNC machined receivers are a thing of beauty, but labor intensive, and inordinately expensive.

Investment casting gives you a receiver that is just as strong, just as durable, and not really very pretty, but at half the cost.

With the prohibitive cost of union labor in this country, in a few decades, forged, machined weapons will be the province of the very rich only.

__________________

Not really. Even if it is cast you still have to machine the critical, functional features. With the amount of material to come off an AR receiver you'll save the time by making it from a solid block vs. trying to fixture a casting. I'll admit there are some very good casting companies out there but by the time you pay for the quality of the casting you could have milled it off. Modern machine centers will remove material at a very rapid pace. We have some machines that will turn a 3/8 carbide endmill at 12,000 rpm. I could, once fixtured up, machine a complete AR receiver in about 20 minutes. Add up the difficulty that fixturing cheaper castings and inconsistencies that you sometimes find with casting compositions it, is most applications just isn't the way to go. I will admit I haven't machined AR castings so I could be off base with this particualr application but as a whole I believe it's an accurate statement.

 

[TonyM1]

That Ferrari will most definitely have forged pistons though, and those are the parts to be concerned about in high performance engines when talking about cast vs forged. Try adding nitrous to an engine with cast pistons, their longevity is greatly inferior to that of forged pistons. Given a choice I would take any piece of machinery with forged rather than cast metal.

 

[Buckythebrewer]

Each one has its place.Its not like cast is junk and forged is great .They both have exact purposes,and usually one is better than the other for different uses.For engines cast cranks are as good or better than forged for many uses,Then you have forged cranks that are not quite as brittle for Higher pressures(for high horsepower applications) but usually tend to not last as long for normal street use..The same goes for pistons,,For normal street use you are much better off with a lighter cast piston than the heavier forged unit.A cast reciever is more than enough for an ar15,Unless you plan on using it for a jack or something it was not designed for

 

[cheygriz]

MXWelch,

My friend, I sincerely hope you're right! Believe me, I prefer forged and CNC milled. I hope that CNC milling can be automated enough to keep making receivers that way forever. But to be prfectly honest, I just don't see it happening. Casting technology is just improving too rapidly.

But again, I would dearly love to be wrong about this.

 

[mxwelch]

Casting technology is just improving too rapidly.

You're right about that, but at the present time all the quality castings we utilize are quite expensive. Castings are beneficial to high quantity production runs where various features aren't nearly as critical. An example would be an engine block vs. a crankshaft. The block isn't to intricate to fixture like a crank would be. The block is usually sleeved as well so material quality isn't critical. The crank however requires top quality to preform to optimal specs. Not a very good example but the best I come up now.

I've seen the reciever process for Rock River (I believe) and they're very efficent.

 

[SavageCheesecake]

Welder here.

Just to throw in another reason why forging is a little better, when a metal is beaten it forces the molecules into alignment. All metals have a certain molecular memory, and one could say that the process of forging programs this memory into its new shape.

Yeah, metals do have crystals. Crystals made of molecules. If it didnt have molecules, it would either be a solid lump of a single base element, or it wouldnt exist.

 

[mooreshawnm]

Thank you for the information guys! Now there is one more thing I can act like I've always known when this eventually comes up with my buddies. It's hard being the one who is supposed to have all the answers : )!

Shawn

 

[BUSTER51]

If you want an AR lower receiver than you want a forged one period. the price differance is small . stick with a CMT or LMT they are the best they are often labled as COLT,BUSHMASTER,STAG,RRA,to name a few .

 

[BillCA]

My metallurgy knowledge is probably out of date, but here's what I've learned over the years.

One reason for forging steel parts is that it is one way to drive out embedded hyrdogen gas that forms pockets in the molten metal.

When you use hydraulic presses to hammer forge hot steel, it compresses the molecular structure together, and drives light hydrogen gas to the surface where it escapes. If the gas does not escape, it forms a pocket which can become a stress point in the steel. Often these pockets are small and/or thin line-like areas. If one of these is too close to the surface of a finished product and subjected to high stress (like firing pressures) the surface can fail, exposing an open "void". This void can be very small but repeated stressing can cause further erosion or failure to contain the stresses resulting in a fracture of the steel. Deeper pockets cause failure when the steel is torqued or flexed and the pocket ruptures, allowing stress to propagate from one area to the next. This is type of failure is termed hydrogen embrittlement.

It was a similar "void" less than 0.5mm in a turbine blade of a DC-10's engine that caused a Delta airliner to crash in an Iowa corn field some years ago.

Some aerospace castings are subjected to vibration and magnetic fields to "settle" the hot steel/alloy and align its crystalline structure. After that, the still warm (hot) casting is then released and compressed in a new mould that is more exacting, under several tons of pressure. The result is a product that is nearly as durable as a forging and suitable for mass produced items in supported structures or non-critical uses.

 

[joshua]

BillCA,

Mete said

forged material is NOT denser. There really isn't any difference between a forged and machined receiver such as a Rem 700 and a high quality investment cast one like the Ruger 77.....Just about all steel is from recycled material regardless of the type !!..Beside , metals don't have molecules !!!

I still pick forged parts if they are available and I can afford them. josh

 

[MacGille]

Forging is stronger and more uniform than casting, The forging process changes the molecular structure of the metal and makes it stronger. HOWEVER, technology is not a static process. Check out MIM ( Metal Injection Molding) parts can be cast to very exact dimensions and In many cases don't require machining. the Metal is forced into a mold under high pressure and I'm told that the results are extremely good. The reason Taurus is able to sell very high quality guns for good prices is their extensive use of this process. Just my 2c worth.

 

[jhgreasemonkey]

Cast reciever AR's? I thought this was a thing of the past because they didnt hold up to well. It seems like all the Ar makers now used forged recievers. Am I missing something here?

 

[Don H]

As I recall, when FN/Browning decided to chamber the High Power in .40S&W, they opted to change from the forged frame the 9mm used to a cast frame in both the .40 and 9mm. Seems to me that if a cast frame was weaker than a forged frame of the same dimensions, FN/Browning would have retained the forged frame to handle the higher pressures the .40S&W develops.

 

[joshua]

Back in the days the metal alloys that can be casted turned out products that were not as strong as forged metal and those cast parts had to thicker than a part that is forged or machined from billet. Nowadays you see plastic replacing metal parts such as receivers in pistols and rifles. I've used MIM parts for 1911s and they have lasted so far. josh

 

[Do_The_Lindy_Hop]

NO, metals do not have molecules!

Welder here.

Just to throw in another reason why forging is a little better, when a metal is beaten it forces the molecules into alignment. All metals have a certain molecular memory, and one could say that the process of forging programs this memory into its new shape.

Yeah, metals do have crystals. Crystals made of molecules. If it didnt have molecules, it would either be a solid lump of a single base element, or it wouldnt exist.

I don't usually contradict people because in most instances, I'm the one who is wrong, but in this case, I beg to differ.

Metals = crystals and crystals are not made of molecules. Crystals and molecules are completely different animals. They have completely different types of bonding mechanism. Crystals are made of atoms STACKED in specific way (Simple cubic, BCC, HCP, FCC, etc) with specific directions in them. Molecules have more complex structures (tetragonal pyramidal, see saw, etc) and organic molecules branch out, making them even more complex in shape. Depends how and where they branch out, they'll named differently (don't ask me how; it's been a long time since my organic chemistry classes).

Bottom line: crystals are not made of molecules.