What are the advantages/disadvantages of uppers and/or lowers machined from billet or forged aluminum?

Forged is typically a piece of material that is smashed into a shape while it is red hot (when referring to a shaped object for rough or final product).
The grain structure of the metal material will follow the shape of the unit being produced.
(ETA: forged material can also have no particular shape to make forged blank material to be machined into smaller pieces but retaining the strength of the initial forge)

Billet is a more general term used to describe a piece machined from a chunk of material/metal.
The original piece is most likely some sort of casting or drawn out, formed piece of metal.

In simple terms forged is probably going to be stronger.
Billet strength is dependent on the original slug of metal it was machined from.

Billet uppers or lowers can be more pleasing to the eye however due to more machining operations to achieve the final product.   A forged or cast piece will usually be a rough resemblance of the final product and some areas may not need a finished surfaced machining/milling.

To add to the confusion you can have a piece that is forged and billet at the same time if the parent material stock was forged.

On another note: Take for instance a crank shaft for an engine that is forged into it's final shape then machined.
The shaped forged crankshaft would be stronger than a crank that was machined from a forged piece of billet material due to the grain structure following the shape of the forging.

Actually forging is the process of smashing the metal to compress the molecules in the steel therefore making the steel much stronger. Sometimes it is forged into shape but that is not necessarily always the case. Most of the time the finished part will be machined from a block or round bar just as it would be from a billet.
the only difference would be that the part machined from the forging would be stronger than the standard billet. Of course this is assuming we are talking about the same parent material.

Are they any functional advantages of getting billet over forged?  They're so much more expensive, but are they at all better?

I have Both.....''SAME SHIT'' ...Billet Looks Cooler

no. buying "billet" is the act of spending more for less.
VLTOR's billet MUR is now a forged MUR and the best upper on the market IMHO. The .mil requires forgings for a reason.

The advantages are in the manufacturing; a forging requires a large initial investment in tooling, but the payback comes in the ability to mass produce consistent, strong parts relatively cheaply on a per item basis.

Manufacturing from a billet (assuming a forged billet) has a lower initial cost investment for the manufacturer since the parts are produced on a one-off basis.  The drawback of this approach is that it takes longer to produce a part, and is therefore more expensive on a per item basis.

The strength issues compared to a forged part can be compensated by adding more material in the billet part, but realistically I don't believe that the strength differences between a forged billet upper/lower and a forged upper/lower are all that great.

In before Wes from MSTN

ETA:  Billet is "prettier" that is all

My machine shop fabricated (machined) structural steel parts for a large manufactuer of commercial airplanes.  The parts were of moderate size with the finished-machined parts weighing 10 lbs or less usually.  Our customer (the airplane maker) provided forgings for those parts, but in every case there was a "bar-stock" option on the part drawing in case the forgings were not available.  The barstock was "forged" from ingots of the same material as the more-net-shape forgings.  The only advantage offered by the forgings was that less material had to be removed to get to the finished part and were therefore cheaper.  The parts were structurally equivalent whether they were machined from forgings which looked, generally like the finished part, or from forged bar which looked generally like "bricks" of 4340M high strength steel.

No, the original piece is a billet.  A billet is an intermediate wrought product between a bloom and finished stock.



Interesting.  Please explain to me the mechanism of molecular compression.  Assuming, of course, that steel had any, which it doesn't.




No.

A billet lower receiver is often finished up into a much more attractive, unique end product than is commonly found in straight forged receivers.

Look at a Sun Devil, Tactical Innovations, or POF billet receivers. Very, very nice looking units. Personally I prefer having at least one or more of my AR's built up on a billet receiver.

I think that because of the ability to add intricate strengthening areas to a billet receiver also makes for a superior product......but I am not a structural engineer.

I forgot to mention the excellen billet lower receivers made by SMOS, that LaRue uses for their Stealth receiver system. A work of art like most billet lowers.

In short billet receivers cost more, look pretty and dont do anything better regular stuff. In short its like jewelry.

Too bad SMOS screwed the pooch by signing up with larue. They would have made a killing with the obama craze  

Always a scientist in the bunch

I was just trying to let the guy know that forging is smashed for strength and doesnt necessarily need to be smashed into any particular shape. Very sorry if my wording was wrong

Especially on a lower. Spending money on something that does exactly DICK!


For some reason, people have yet to figure out that the lower does nothing but house the trigger assy, contain 2 takedown pins that have ZERO stress on them, and hold a stock. Thats it.


Its like having an even tougher, pimped out, polished sledge hammer.

better, but why?

Would you say the same with respect to comparing cast and forged lowers?

Why or why not?

I guess I should have been more clear.
I know the definition of billet.  But for this conversation the OP is referring to a billet upper or lower.
The seller of billet lowers, uppers, receivers often refers to them as "billet lowers" for marketing purposes.  Same as many manufacturers refer to forged pieces as "forged steel" "forged aluminum" etc. etc.

Instead of picking apart everyone's posts maybe you can write up a little piece on billet vs. forged.

Not at all.

A forged lower is something you want, but a billet milled one is overkill.
Cast is weaker, and more brittle. And is just like the name says. Its "cast" into a mold.

Think pot metal on your gun. Avoid.

Which is why I went all scientist on you.  Billets are the product that is forged in no particular direction (open die or rolling mill).  The parts that you usually see described as "forged" are actually closed-die forgings, meaning that the stock is forged to a near-net shape and avoiding re-entrant flow lines, which means that the directionality of the grains flow with the shape of the part, which in turn minimizes anisotropy in the component.

So a part described as "forged" in AR-15land is indeed usually smashed into a particular shape.



Seems to me I have written lengthy posts on the cast vs. forged vs. billet threads on multiple occasions, on multiple boards.  I am not going to do it everytime the topic comes up.

Battle, how about requesting a sticky?  I agree it would be very useful.

use the archives, cut/paste, but this would be valuable.

How bought a link?

AGNTSA? From an earlier thread (AHEM, Mods, a tack?)

http://www.ar15.com/forums/topic.html?b=3&f=118&t=413585

Forged, any day, will be stronger on a lower. Why? The weakest part is the buffer tube ring at the rear of the lower. Here, the forged lower has a flowed grain structure optimized for the area.

Hogged out of bar stock, the grain of the metal is like that of straight-grained wood. Entirely wrong for the part. With good quality 7075 aluminum, you can get away with it. But how many are actual Kaiser/ALCOA/Renyolds with Certified Mill Test Reports? And how do you know the grain direction? You are at the mercy of the machinist who may or may not know about aluminum microstructure.

Now let us look at the typical Mill Test Report for aluminum. Firstly, there is the chemical analysis. This tells us the alloy. Then there is the temper designation. We want T6. No need in having to send it out for heat treat as then more testing. Then we have tensile testing.

Now for the fun part. Tensile testing. This part of the MTR will have at least two, if not three tensile specimen axes. Not the Paul Bunyon tree felling implement but the direction in which the samples are loaded. There will be specified minimums, yield point, enlongation and ultimate tensile strengths reported. For sheet products, there is typically only two tensile coupons and a shear but for plate/bar, there can be three tensile tests. Since the lower is subjected to triaxial stress with associated moments, it would be a good idea to insist on knowing these properties.

But in a forging? Part of the quality process is complete tensile testing of the rough forging and sample coupons have been taken from a representative part.

Since non-destructive testing on aluminum is limited to RT/UT/PT and all but PT are specialized practices, buying a receiver hogged out of bar/plate is a gamble. I would suggest a copy of the mill test report.

And despite the over misuse of the term "billet". I continue to call these plate machinings. Why not billet? Because a billet is a raw mill product without any wrought processing. Billets are technically CASTINGS and not what the machine shop or even forging plant uses as raw material. Forgings are made from BAR STOCK which is a wrought product form.

Anodizing does NOTHING to strength. It is brittle, being a form of aluminum oxide not unlike that common abrasive on sandpaper. It is flat, solid ceramic made from the aluminum itself so it has great adhesion.

In the M16 series, the upper only holds the pieces of the rifle together and forms a guide for the bolt carrier. Because the only real sliding force contact is the carrier key's reaction to bolt locking/unlocking torque, this is the only real wear area. The sliding forces of the carrier are very low, representing only the misalignment of the carrier. Since the carrier key slot is protected from dirt, this causes the carrier's rails to exhibit the greatest wear even though steel is much harder than aluminum. The anodization polishes the rails slowly. In proper treated uppers, a layer of moly disulfide dry film lube keeps this wear minimal.

In fact, hard anodization can form surface crack propagation, lowering fatigue life. But this is not significant in the M16 series as there is sufficient ductility and the receivers are subjected to very low cyclic stress.

Hard anodization is a durable finish, resistant to most abrasion from normal "sling type" wear. But being brittle, impact with hard surfaces will cause failure. The military refinishes with moly disulfide dry film lubricant, all over.

For those of you who received an email from Ranier Arms about their billet uppers and the grade of aluminum used, what do you think about it?

first pic?



any day of the week!!!IMHO

I always thought that billet was stronger. It does look better too

If billet is like jewelry, will I get laid more if I give my girl friend a billet AR instead of a forged one?

The problem with "billet" parts is that you don't know anything about the metal blank they started with before machining it.  It could have been a chunk of aluminum that was forged as a flat chunk and then CNC milled away "everything that didn't look like a receiver."  Or it could have been a chunk of aluminum cut from a big slab.  That's a big difference in potential strength!

On the other hand, a forged receiver is forged in the basic shape of the receiver, so the crystalline alignment conforms to many of the shapes (especially the curves) of the final product, making it (theoretically) stronger.  Since some of those curves (like the front end of an upper receiver) are "kind of important," I personally think this process makes for a stronger and more reliable part.  Assuming it's milled properly, of course.

I don't quite understand.  From my understanding, a billet is a raw materials that is cast - nowadays mostly through continuous casting process from the melt shop.  It has not been rolled; the microstructure is still divided into three distinct regions.  After the billets are cast, they can then be "hot charged" directly from the caster's table to the rolling mill or they can be stacked for later use.  Maybe the term "billet" is different in the aluminum industry than that used within the steel industry?

As with forgings - it is the grain "texture" that flows with the work piece, but the grain structure itself is equi-axed crystalline due to recrystallization process at the elevated temperature.  It will still exhibit anisotropy due to the textural flow of the grain, but the equiaxed grain structure will minimize the degree of this anisotropy, as you have mentioned above.

I am not familiar with the type (size, microstructure, grade, etc) of the billets they use to make these receivers, so I have a question.  Is this a concern: anisotropy and possibly severe mechanical properties differences at different parts of the receiver due to the distinct types of microstructure that can be found throughout a billet.    How many tensile tests do they form on the billet - on all three axis and were samples taken from different sections of the billets?

And people, may I suggest that we refrain from using the term "molecule" when addressing metallic structure and use the term "crystalline structure" instead?  Just a suggestion.

Edited for clarity (well, I tried anyway )

Yep, on those curved parts, the stringers that formed the fiberite texture due to the forging process could act as crack arrestors.  Good call!

Keith_J leads the way AGAIN!  This is a thread to end all threads when it comes to forged Vs. billet receivers.  Memorize it, people - exam tomorrow!  

That's a good point, but if you machined a receiver out of a billet, you don't know from which part of the billet that receiver was machined out of.  Did they take samples from different parts of the billets to ensure tensile strength uniformity?  From all three axes?  A tensile sample composed of microstructure primarily from the chill zone will have a different value than that taken from the columnar zone of the billet?  Unless if the billet they used in the manufacture of the receiver is tightly controlled in temperature and with the addition of inoculants / alloying elements combined with relatively small size in order to promote the formation of equiaxed zone toward the middle of the billet instead of the columnar zone.

And I have yet another question - how come there were so much problems with cast aluminum receivers made for ARs? What are the differences between a receiver machined out of a billet, which is a cast product, and a receiver that was cast in a mold?


NEVER MIND!  My question had been answered:




I am a flunk, I know!

Are you sure they are not bar stock?

I got the email your referring too, and let me just say I love the guys at rainier, bought tons of things from them, will continue too, but that email was kinda knocking down the MUR and made their billeted Upper seem like it's 10X better than anything out there and that was the only thing I didn't like. Their customer satisfaction was through the roof in the sense that if you don't like it we'll refund your money back no questions asked, but I don't need an upper at this point in time and if I did I'd probably get another MUR, just my 2 cents.

There is no advantage as far as strength goes billet vs. forging on an AR.
Either is only as good as the quality put into the manufacturing process.

You do not see forged parts on AIRPLANES critical airframe parts. I work with Manufacturers starting with a
100lb. piece of aluminum and ending up with a 16lb part as an example

If you were using a forging, it would be forged to NEAR NET shape meaning a lot less machining
is required to produce the part. In the example above a 25lb forging may be requred to produce the 16lb part.

The advantage to forging is the money saved in machining. On an airplane on the frame parts you don't want
a material flow as in a forging. Those layers can delaminate under stress. You will not see this on an AR as the
stresses are not enough.

You can get forged/machined AR  uppers/lowers for less money as there is less machining involved and rest assured it's as strong as
one machined from a billet. Price is the determining factor along w/appearance. Functionality no difference unless you are going
to try and build an airframe with them and fly then I'd go w/billet.

OH one other thing I keep seeing is people think billet is cast, it is not.
Castings are cast.
Billet is not anything near a casting.  They are as far apart as left is to right.

What?  So how were billets produced from the melt shop if not through the casting process?

If the material delaminates, that is not because of the forging process.  Materials that are extruded or drawn can delaminate along the grain boundaries, but not in equiaxed crystalline structure you see in forging.  The fiberite texture that flows through the work piece is the product of stringers; that is not the grain structure itself; those stringers, however, are ductile inclusions that can actually benefit in stopping crack propagation.  Torsion tests reveal this quite easily - all forging samples should have a flat, ductile failure during torsion tests indicating transgranular fracture - if it has 45 degrees fracture surface during a torsion test, the inclusion must have been brittle or the piece suffers from grain boundary embrittlement - not because of the forging process.

Depending on what aircraft part you're talking about, you WILL see forged parts.  Any part that sustains significant stress could be forged.  Landing gear parts and engine mounts are two examples where, depending on the aircraft and application, you might see forged parts.  And those raw forgings, as with AR receivers, come out close to the final GROSS shape.  But also like with AR receivers, a BUNCH of material is milled away, creating VERY strong, and very light parts.

Extrusion!  (what do I win?)