Milled Vrs. Forged????


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Old Glory
December 6, 2008, 03:14 PM
Some receivers are milled others are forged. Is there a difference? Is one better than the other???

Clarification needed.

Thanks in advance

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RyanM
December 6, 2008, 03:20 PM
Forging means the metal is heated up, then whacked until it's the right shape. In the gun industry, it's usually drop forging. A piece of metal's heated up, put in one side of a die, then the other die is dropped onto it with a huge weight attached.

Then the forging is milled/machined to the final shape.

Plain "milled" receivers start out with extruded bar stock, which is heated and then squeezed through a hole, or between rollers, or whatever, depending on the specific bar stock.

Forgings are usually stronger. With the AR-15, stick with forged lowers only. There are companies that say milled AR lowers are stronger, but they're full of crap. You want everything aluminum to be forged, on an AR. Receivers, carry handle, charging handle, front sight base, etc.

RockyMtnTactical
December 6, 2008, 03:22 PM
Yep, forged is better/stronger.

1858
December 6, 2008, 03:36 PM
Forging means the metal is heated up, then whacked until it's the right shape.

Metals and alloys can be cold forged too. Rebar is cold forged. There are hybrid processes where the metal/alloy is heated to solid solution temperature and then "squeezed" into the desired shape. Some automotive rims are made this way.

Basically, forging produces some of the strongest parts because it generates lots of dislocations inside the material. When a material changes its shape (permanently) under load, this is called plastic deformation. To deform a metal/alloy part under load, the internal atoms/molecules need to slip along nicely ordered planes like pages in a phone book . If there are dislocations mixed in with the ordered planes (imagine stapling numerous pages together), then the planes can't move as easily which means the part isn't as easy to deform.

:)

P.S. Milling is generally a lot more time consuming and wasteful compared to forging but with modern alloys such as Al 2024-T3, Al6061-T6 and Al7075-T6 and their respective heat treatments, milling can produce VERY strong parts to exacting tolerances with numerous cold-worked surfaces.

taliv
December 6, 2008, 04:02 PM
also the milled stuff is usually a good bit thicker in places.

the questions are: how strong does it NEED to be? and how close do the tolerances NEED to be?

imho, the milled and forged receivers both greatly exceed the reasonable requirements for AR15 parts, so it comes down to a question of weight and cost to me, as long as there aren't special requirements, like minimizing flex in the upper.

30Cal
December 6, 2008, 04:17 PM
Assuming the receiver is built to print, forged is better.

Gordon
December 6, 2008, 04:29 PM
The forged pieces are generally cleaned up my milling, BTW !

CSestp
December 6, 2008, 04:44 PM
Only reason a forged part is stronger is because it is normally heat treated, as it is just part of the prosscess of forging something. If you get a milled part that has been heat treated to the same specs as the forged part I would have to say the milled is going to be stronger.

This is just a metal workers opn. on metal in general, but I'm sure the same laws of physics apply to the gun world as they do the metal world.

Shear_stress
December 6, 2008, 04:45 PM
The forged pieces are generally cleaned up my milling, BTW !

Exactly. Forging and machining are not mutually exclusive. When it comes out of the forge, a workpiece only vaguely resembles the final product and must go through several machining operations to achieve the final dimensions. In firearms, forging has more to do with getting the desired grain structure than in shaping the part.

1858
December 6, 2008, 05:09 PM
Only reason a forged part is stronger is because it is normally heat treated

Do you mean heat used in the forging process or heat applied after? Read my post above ... the "strength" of forged metals/alloys has NOTHING to do with the heat used for the forging process. How come cold working steel makes it "stronger"? In fact, rebar has to be bent using a cold process ... ask any civil engineer on a construction site if you can use an oxyacetylene torch to heat up and bend some rebar before you pour the concrete!

Heat treatments do produce stronger alloys by such phenomena as precipitation hardening but that's not what is going on during a forging process. In fact, parts are often HEATED AFTER forging in an annealing process which "removes" the dislocations mentioned above.

:confused:

tblt
December 6, 2008, 05:12 PM
milled is alot better

Cesiumsponge
December 6, 2008, 05:22 PM
Everything has it's place. Being in the aerospace manufacturing industry, I can say many important airplane parts are milled and turned from metal stock or castings. That doesn't seem to bother Boeing 777s or F-22 Raptors.

There seems to be mythical qualities behind manufacturing processes when firearms are concerned...anywhere from mystical 4140 "firearms/match grade" steel (which is a generic steel in the manufacturing industry) to magic coatings like TiN which is decades behind the best VPD coatings being used on high wear industrial tooling. I don't know if this is due to reading one too many magazines or unfamiliarity with manufacturing.

As mentioned, the strength benefits/detractors of milling vs forging are magnitudes above what stress an AR15 receiver would ever see. If it was really that critical to it's threshold of failure, we would be using steel for AR receivers. I've also never seen any post-machining heat treat processes for aluminum like that for ferrous metals. That stuff comes to us from places like Alcoa with a temper code already (6061-T4, 6061-T6. etc). Normally after completion of machining, it gets anodized or plated.

RyanM
December 6, 2008, 08:24 PM
As mentioned, the strength benefits/detractors of milling vs forging are magnitudes above what stress an AR15 receiver would ever see.

One which never sees anything but the range and the inside of a safe, maybe. One that's dropped, stepped on, used to bust heads, etc., may require slightly stronger materials.

And steel is too heavy.

taliv
December 6, 2008, 08:45 PM
what kind of strength, ryan? tensile? shear? compressive? are you sure forged excels in all those categories?

can you quantify how much strength is needed? what are the specs of the requirements?

jpwilly
December 6, 2008, 08:48 PM
milled is alot better

Eventually every forging is milled unless it's a stamped part like the AK reciever. Cast parts on the other hand are a completely different story.

Cesiumsponge
December 6, 2008, 09:34 PM
One which never sees anything but the range and the inside of a safe, maybe. One that's dropped, stepped on, used to bust heads, etc., may require slightly stronger materials.

You're making the receiver from identical material. Is there a conclusive study that says milled receivers can't take the stress? The firearms world is no different than any other consumer market. You have marketing departments pushing buzzwords that people buy into. A proper temper and certified material is more critical than forging or milling processes. Radiusing edges to prevent internal stress risers (which lead to cracking) is more important.

How many firearms companies explicitly market the fact they are ISO9001 certified or use lab-certified materials and ISO vendors? Or that their receivers are fully radiused to prevent internal stress risers? None, because they aren't sexy marketing buzzwords. They are if you're an engineer looking to procure services, but to the consumer...not very important. However "forging" sounds sexy. It sounds strong. It's easier to market. The same marketing people love to put "aircraft grade" in front of every aluminum alloy they use or "match grade" in front of every stainless or cro-mo steel they use, as if their competitors use "pot metal grade" aluminum and "plinker" grade steel.

I have an AR receiver whereby the magazine well was machine broached to final size which leaves an incredibly uniform surface. Is it superior? Yeah, very likely. Does it make a practical difference? Not really.

Also this might blow your mind, but forged receivers can be much cheaper to manufacture than an identical item milled from a solid aluminum block. It also results in less waste material which saves the manufacturer money. The initial tooling costs to manufacture the forging dies is quite high, but forging is ultimately a mass production method that gets cost-per-unit far below that of milling it from a raw block, which requires more extensive tooling and multiple setups, and a lot more time, waste management, and floor space. Looking at the complexity of an AR receiver, it can easily take several hours to mill just one receiver using an automated palletized system. Forging ultimately creates a receiver that is perhaps 75% finished and requires milling a few spots, and reaming a few holes.

It saves time and money, and any positive material properties are a side-effect.

RyanM
December 6, 2008, 09:57 PM
Also this might blow your mind, but forged receivers can be much cheaper to manufacture than an identical item milled from a solid aluminum block.

You are being really freaking condescending.

Anyway, yes, I know full well forging, in this case, is way cheaper (especially for parts with rounded edges) and wastes way less material (for aluminum, anyway).

However, it's still entirely possible that forging results in a stronger receiver in this case.

Small things like that can make a difference.

This might blow your mind, but temperature makes a difference for the strength of extruded material, even when the material is identical (I couldn't find data on forged vs. extruded stock, nor hot vs. cold for the alloy ARs are made of, at least not in a 5 minute search on matweb).

http://www.matweb.com/search/DataSheet.aspx?MatGUID=28e2a176e2274a8d8978302413ae9075&ckck=1
http://www.matweb.com/search/DataSheet.aspx?MatGUID=e971f0e9181e4b5596428047c45648e1

For impact extruding a cylinder, anyway, cold results in slightly stronger stock than hot.

Cesiumsponge
December 6, 2008, 11:02 PM
No one is saying forging makes a weaker product. At least, I never made that claim. I have stated the benefits of one other the other is minimal considering all other aspects that are infinitely more important in the overall product's integrity. Looking at the extrusion tangent, the differences between those figures is on the order of 2-4%, a tiny margin that probably wouldn't make a real world difference in designing a product considering all other factors.

If you're going to call those two extruded products, finished with different techniques from the material supplier, "identical", then I have an issue with that. They are identical only in chemical composition only and not structure. As a product you buy from the supplier, they are not identical at all. If you were AS/ISO, they would be lab certified as two different materials.

You're not likely going to find forged data from the Matweb material database because material suppliers don't create forged metal stock as it would be senseless. Materials come out of mills in extruded, rolled, plate, and drawn form (maybe a few others I missed). Forging is a manufacturing process outside of the supplier to get metal stock to very specific shapes, and properties vary depending on the size, shape, and complexity of the item and where you measure the item. I just don't see why you're putting all this emphasis on forged parts.

With the AR-15, stick with forged lowers only....You want everything aluminum to be forged, on an AR. Receivers, carry handle, charging handle, front sight base, etc.

Are you serious...I have to replace my carry handle with a forged carry handle because mine is inferior enough that there will be a quantifiable difference? Unless we see a rash of milled receivers cracking and breaking under identical conditions as forged receivers, then claiming:
One which never sees anything but the range and the inside of a safe, maybe. One that's dropped, stepped on, used to bust heads, etc., may require slightly stronger materials. has no real quantifiable merit.

I'm pretty sure my Geiselle DMR match trigger appears to be a cast investment. This whole "forged vs milled" issue has been discussed ad nauseum on -that AR forum- and there are no conclusive results either. Googling for "forged vs milled" on the internet shows mostly nothing except threads on AR lowers. Nothing in aerospace, nothing in automotive, nothing commercial, industrial, or otherwise. A couple hits on golf clubs. You know what that probably suggests? It doesn't really matter.

Ignition Override
December 6, 2008, 11:40 PM
Cesiumsponge:

But composite components, as with the A-300's vertical stabilizer, can't easily be taken apart and inspected as with the 737-200 and 400 etc., if I understood written descriptions. But I'm not an engineer.

Although having nothing to do with guns, this disadvantage was reported in Aviation Week, regarding the AMR disaster near JFK.
Stress during major temperature changes from the gate to FL 350 might have created weaknesses?
As for serious rudder anomalies, former (DDR/East German) Interflug, Air France and Air Transat had mysterious rudder anomalies enroute, but those were not fatal.
On Air Transat the rudder almost seperated. "Merci...au 'revoir".
And the 300/310's rudder movement is reportedly very disproportionate for a given amount of rudder pedal travel.
Not so on the 'steam-gauge' DC-9 etc, and the speed-controlled rudder limiter does a good job, having no computerized systems to rely on (just right hydr. pressure {> 950 psi} and a basic control tab for back-up).

Back to guns.

Loomis
December 6, 2008, 11:52 PM
i don't know about aluminum, but steel has a grain just like wood. Forged steel is superior to milled steel because when you forge it, the grain is bent around the curves of the part you just made. Just as wood, steel is weaker in one direction than the other because of the grain structure. So when the grain follows the curve of the part, it is stronger than if it doesn't. Imagine an archer makes a bow out of a 2x4. If he softens the 2x4 and forces it to the curve of the finished bow, then trims off the exess wood, he has a good strong bow. If he starts with a straight 2x4 and cuts away everything that isn't a bow, the resulting bow is weak because the grain of the wood doesn't follow the curve of the bow.

Cesiumsponge
December 7, 2008, 01:51 AM
Ignition Override:

I've never worked with aerospace composite stuff so I couldn't give any educated opinion on that matter at all. All that crazy stuff is unobtainium to me.

Loomis:

I don't think most people here dispute that forging can enhance properties, but the question on aluminum receivers is to what degree, and is that additional enhancement actually utilized in the duty cycles seen by AR rifles? We don't (at least I haven't) seen any of the forging vs milling debates on any other subject within the gun community. I don't even see it in manufacturing or commercial products besides the AR15 and AK receivers. I just find that a tad suspect.

Also, the enhancements by forging assume the manufacturer is purchasing their material and specifically getting suppliers to mark the grain orientation of the raw barstock correctly as it's coming off the rollers. Some people might be forging for the sake of economics and loading cubical slabs to be forged without regards to grain orientation. In aerospace, certain parts being machined indeed have a grain orientation call out on engineering prints and all the material coming in must be marked, but this isn't as typical in the commercial industry.

SHvar
December 7, 2008, 03:03 AM
Will cave in someone skull just as easy, and no damage will occur to either rifle parts.
I dont really care if theres a minute difference between the strength of them, for the purpose of use in a rifle both are far stronger than needed, in fact both could be interchanged in battle without any difference unless you use your rifle as a sword exclusively. Im sorry a rifleman protects his rifle, his life depends on that rifle functioning, its not a broad sword.
If I wanted to club my enemy to death Id take his dirty AK-47 and beat him with it.

moooose102
December 7, 2008, 08:06 AM
forgings are stronger. most all of them are machined afterwards due to the tight production tollerences. forging compresses the metal, so in essence, you are getting more metal compressed into the same space. this molecularly pushes the grains closer together and eliminates any places where the grains were loose or farther apart(weak spots). forgings will take much more stress in every direction as well as heat/cold fluctuations. stress relieving (which is a series of heating and cooling) , or cryo treating (which is where they dunk the part in liquid nitrogen and then warm it back up) also helps strengthen the metal. a part that has been stress relieved is way less likely to warp from heat, as it will have already had all of its grains aligned into shape during the process. then the part is machined, and you have one tough cookie. i do not know how much of this goes on in rifle/pistol manufacturing. but you can bet if you buy a $250.00 gun, not a lot of it has. it cost money to do all of these things, and somebody has to pay for it. it is not going to be the manufacturer. he is going to pass those costs on to you.

Evil Monkey
December 7, 2008, 09:15 AM
Milled forged extruded aaaaaaaaahhh non sense!

Put the damn steel sheet in the stamping press....BAM!....put it in the oven and bake at 375 degrees.

gvnwst
December 7, 2008, 09:37 AM
forging compresses the metal

IIRC, metal, being a solid, cannot be compresssed. What forging does is re-align the grain structure of the metal, (*possibly* it does get more compact because of the realighing) which makes it stronger. In the automotive industry, the pistons for high performance cars are forged, with the grain facing up to down, to allow the pressure to be evenly distrubited. I hope the firearms companies do the same, or something close.

Art Eatman
December 7, 2008, 10:00 AM
Lordy, lordy. The poor guy's question was answered fairly early on and now we have a half-page of squabbles over details? Gimme a break!

It's Sunday morning. Go to church, or prep for an afternoon at the range. Go hunting.

Don't squabble.

Enuf.

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